Possibilities Cube Library - A Library Smart Enough To Calculate All Possibilities With Logical Conditions

Let's imagine that as a big advertisement campaign Vodafone, Samsung & Nokia co-arranged a lottery. The winner will get two mobile phones in addition to two SIM cards with special numbers.

It is obvious that the SIM cards will be provided by Vodafone while the mobile phones manufacturer will be decided by toss, so the winner may get two phones from Samsung or Nokia or both. Also, the phones specifications will be somehow restricted as in the image below.
 

So, if we try to guess all the possible combinations of any of the phones, we can work it out and get the results as in the image below.

This was somehow easy as the possibilities are not that large. But what about guessing all the possible combinations of the two phones at the same time?

This time it is not that easy due to the large number of possibilities. As we can see there are 64 possibilities and this is because each phone can be one of 8 phone combinations and we have 2 phones, then 8 * 8 = 64

What if I told you that we need to re-visit the phones combinations are there is something not logical. We know that Samsung doesn't produce phones with Symbian as OS. So, we need to cancel the phone combination which includes both Samsung and Symbian.

Also, if the lottery managers said that the two mobile phones can't be identical or exactly the same which means that at least one phone specification should be differ between both phones.

All these logical restrictions should be included in our calculations to finally get all possible combinations we need.

If we try to visualize the whole thing, we can see it into the image below.

Now, how about if I tell you that there is a library which you can use to calculate such calculations and you can define your own logical restrictions to filter out all logically refused combinations, will you like to use this library?

Here come the PossibilitiesCube library.


PossibilitiesCube.cs

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;

namespace DevelopmentSimplyPut.CommonUtilities
{
    public class PossibilitiesCube
    {
        #region Properties
        public Func<Int64[], bool> AttributesCombinationValidator { set; get; }
        public Func<Int64[], bool> InstancesCombinationValidator { set; get; }
        public Func<Int64[], Int64[,], bool> FinalCombinationValidator { set; get; }
        public Int64 InstancesCombinationsMaxRowIndex
        {
            get
            {
                return instancesCombinations.GetLength(0) - 1;
            }
        }
        public Int64 InstancesCombinationsMaxColumnIndex
        {
            get
            {
                return instancesCombinations.GetLength(1) - 1;
            }
        }
        public Int64 AttributesCombinationsMaxRowIndex
        {
            get
            {
                return attributesCombinations.GetLength(0) - 1;
            }
        }
        public Int64 AttributesCombinationsMaxColumnIndex
        {
            get
            {
                return attributesCombinations.GetLength(1) - 1;
            }
        }

        bool combinationsExist;
        public bool CombinationsExist
        {
            get
            {
                return combinationsExist;
            }
        }
        #endregion Properties

        #region Fields
        Int64 numberOfInstances;
        Int64 instancesCombinationsMaxRowIndex;
        Int64 instancesCombinationsMaxColumnIndex;
        Int64 attributesCombinationsMaxRowIndex;
        Int64 attributesCombinationsMaxColumnIndex;
        Int64[,] attributesCombinations;
        Int64[,] instancesCombinations;
        Int64[] attributesPoolsSizes;
        #endregion

        #region Indexers
        public Int64 this[Int64 instancesCombinationIndex, Int64 instanceIndex, Int64 attributeIndex]
        {
            get
            {
                return GetAttributesCombination(instancesCombinations[instancesCombinationIndex, instanceIndex])[attributeIndex];
            }
        }
        public Int64[] this[Int64 instancesCombinationIndex, Int64 instanceIndex]
        {
            get
            {
                return GetAttributesCombination(instancesCombinations[instancesCombinationIndex, instanceIndex]);
            }
        }
        public Int64[] this[Int64 instancesCombinationIndex]
        {
            get
            {
                Int64[] result = new Int64[instancesCombinations.GetLength(1)];
                for (Int64 i = 0; i <= instancesCombinations.GetLength(1); i++)
                {
                    result[i] = instancesCombinations[instancesCombinationIndex, i];
                }
                return result;
            }
        }
        #endregion

        #region Constructors
        public PossibilitiesCube(Int64 _numberOfInstances, params Int64[] _attributesPoolsSizes)
        {
            if (_numberOfInstances <= 0)
            {
                throw new Exception("NumberOfInstancesPerPossibility must be +ve and greater than 0.");
            }

            numberOfInstances = _numberOfInstances;
            attributesPoolsSizes = _attributesPoolsSizes;

            attributesCombinationsMaxRowIndex = 1;
            foreach (Int64 size in _attributesPoolsSizes)
            {
                attributesCombinationsMaxRowIndex *= size;
            }
            
            attributesCombinationsMaxRowIndex--;
            attributesCombinationsMaxColumnIndex = _attributesPoolsSizes.Length - 1;
        }
        #endregion Constructors

        #region Methods
        public Int64[] GetAttributesCombination(Int64 index)
        {
            Int64[] result = new Int64[attributesCombinations.GetLength(1)];

            for (Int64 i = 0; i < attributesCombinations.GetLength(1); i++)
            {
                result[i] = attributesCombinations[index, i];
            }

            return result;
        }
        private void GetPossibilities()
        {
            Int64[,] result = new Int64[instancesCombinationsMaxRowIndex + 1, instancesCombinationsMaxColumnIndex + 1];
            Int64 numberOfFilteredOutPossibilities = 0;

            for (Int64 i = 0; i <= instancesCombinationsMaxRowIndex; i++)
            {
                Int64[] rowResults = GetPossiblityByIndex(i, instancesCombinationsMaxRowIndex, instancesCombinationsMaxColumnIndex, InstancesCombinationValidator, OperationMode.Instances);

                if (rowResults[0] == -1)
                {
                    numberOfFilteredOutPossibilities++;
                }
                else if(null != FinalCombinationValidator)
                {
                    if(!FinalCombinationValidator(rowResults, attributesCombinations))
                    {
                        rowResults[0] = -1;
                        numberOfFilteredOutPossibilities++;
                    }
                }

                for (Int64 k = 0; k < rowResults.Length; k++)
                {
                    result[i, k] = rowResults[k];
                }
            }

            Int64[,] finalResult;
            Int64 actualNumberOfPossibilities = instancesCombinationsMaxRowIndex + 1 - numberOfFilteredOutPossibilities;

            if (actualNumberOfPossibilities > 0)
            {
                finalResult = new Int64[actualNumberOfPossibilities, instancesCombinationsMaxColumnIndex + 1];

                Int64 actualRowIndex = 0;
                for (Int64 i = 0; i < instancesCombinationsMaxRowIndex + 1; i++)
                {
                    if (result[i, 0] != -1)
                    {
                        for (Int64 k = 0; k < instancesCombinationsMaxColumnIndex + 1; k++)
                        {
                            finalResult[actualRowIndex, k] = result[i, k];
                        }

                        actualRowIndex++;
                    }
                }

                combinationsExist = true;
            }
            else
            {
                finalResult = new Int64[1, instancesCombinationsMaxColumnIndex + 1];
                for (Int64 k = 0; k < instancesCombinationsMaxColumnIndex + 1; k++)
                {
                    finalResult[0, k] = -1;
                }

                combinationsExist = false;
            }

            instancesCombinations = finalResult;
        }
        public void BuildPossibilitiesMatrix()
        {
            Int64[,] result = new Int64[attributesCombinationsMaxRowIndex + 1, attributesCombinationsMaxColumnIndex + 1];
            Int64 numberOfFilteredOutPossibilities = 0;

            for (Int64 i = 0; i <= attributesCombinationsMaxRowIndex; i++)
            {
                Int64[] rowResults = GetPossiblityByIndex(i, attributesCombinationsMaxRowIndex, attributesCombinationsMaxColumnIndex, AttributesCombinationValidator, OperationMode.Attributes);

                if (rowResults[0] == -1)
                {
                    numberOfFilteredOutPossibilities++;
                }

                for (Int64 k = 0; k < rowResults.Length; k++)
                {
                    result[i, k] = rowResults[k];
                }
            }

            Int64[,] finalResult;
            Int64 actualNumberOfPossibilities = attributesCombinationsMaxRowIndex + 1 - numberOfFilteredOutPossibilities;

            if (actualNumberOfPossibilities > 0)
            {
                finalResult = new Int64[actualNumberOfPossibilities, attributesCombinationsMaxColumnIndex + 1];

                Int64 actualRowIndex = 0;
                for (Int64 i = 0; i < attributesCombinationsMaxRowIndex + 1; i++)
                {
                    if (result[i, 0] != -1)
                    {
                        for (Int64 k = 0; k < attributesCombinationsMaxColumnIndex + 1; k++)
                        {
                            finalResult[actualRowIndex, k] = result[i, k];
                        }

                        actualRowIndex++;
                    }
                }

                instancesCombinationsMaxRowIndex = intPow(actualNumberOfPossibilities, numberOfInstances) - 1;
                instancesCombinationsMaxColumnIndex = numberOfInstances - 1;
            }
            else
            {
                finalResult = new Int64[1, attributesCombinationsMaxColumnIndex + 1];
                for (Int64 k = 0; k < attributesCombinationsMaxColumnIndex + 1; k++)
                {
                    finalResult[0, k] = -1;
                }

                instancesCombinationsMaxRowIndex = 0;
                instancesCombinationsMaxColumnIndex = 0;
            }

            attributesCombinations = finalResult;
            GetPossibilities();
        }
        private Int64[] GetPossiblityByIndex(Int64 rowIndex, Int64 maxRowIndex, Int64 maxColumnIndex, Func<Int64[], bool> validator, OperationMode mode)
        {
            Int64[] result = null;

            if (rowIndex >= 0)
            {
                if (rowIndex <= maxRowIndex)
                {
                    result = new Int64[maxColumnIndex + 1];

                    for (Int64 i = 0; i <= maxColumnIndex; i++)
                    {
                        result[i] = GetPossiblityByIndex(rowIndex, i, maxRowIndex, maxColumnIndex, mode);
                    }

                    if (null != validator)
                    {
                        if (!validator(result))
                        {
                            for (Int64 i = 0; i <= maxColumnIndex; i++)
                            {
                                result[i] = -1;
                            }
                        }
                    }
                }
                else
                {
                    throw new Exception(string.Format("rowIndex can not be greater than {0}", maxRowIndex));
                }
            }
            else
            {
                throw new Exception("rowIndex must be +ve or equal to 0.");
            }

            return result;
        }
        private Int64 GetPossiblityByIndex(Int64 rowIndex, Int64 columnIndex, Int64 maxRowIndex, Int64 maxColumnIndex, OperationMode mode)
        {
            Int64 result = 0;

            if (rowIndex >= 0 && columnIndex >= 0)
            {
                if (rowIndex > maxRowIndex)
                {
                    throw new Exception(string.Format("rowIndex can not be greater than {0}", maxRowIndex));
                }
                else if (columnIndex > maxColumnIndex)
                {
                    throw new Exception(string.Format("columnIndex can not be greater than {0}", maxColumnIndex));
                }
                else
                {
                    Int64 numberOfHops = 1;
                    Int64 numOfItems = 1;

                    switch (mode)
                    {
                        case OperationMode.Attributes:
                            numOfItems = attributesPoolsSizes[columnIndex];
                            if (columnIndex == 0)
                            {
                                numberOfHops = 1;
                            }
                            else
                            {
                                numberOfHops = 1;
                                for (Int64 i = 0; i < columnIndex; i++)
                                {
                                    numberOfHops *= attributesPoolsSizes[i];
                                }
                            }
                            break;
                        case OperationMode.Instances:
                            numOfItems = attributesCombinations.GetLength(0);
                            numberOfHops = intPow(numOfItems, columnIndex);
                            break;
                    }

                    result = GetPossiblityByIndex(numOfItems, numberOfHops, rowIndex);
                }
            }
            else
            {
                throw new Exception("rowIndex and columnIndex must be +ve or equal to 0.");
            }

            return result;
        }
        private Int64 GetPossiblityByIndex(Int64 numberOfItems, Int64 numberOfHops, Int64 rowIndex)
        {
            Int64 result = 0;
            result = rowIndex / numberOfHops;
            result = result % numberOfItems;
            return result;
        }
        private Int64 intPow(Int64 a, Int64 b)
        {
            Int64 result = 0;

            if (0 == b)
            {
                result = 1;
            }
            else if (1 == b)
            {
                result = a;
            }
            else
            {
                result = a;
                for (Int64 i = 0; i < b - 1; i++)
                {
                    result *= a;
                }
            }
            
            return result;
        }
        #endregion Methods
    }

    public enum OperationMode
    {
        Attributes = 0,
        Instances = 1
    }
}

How to use the library?
The library is somehow simple in usage but always keep in mind the complexity of the task it is about to carry out. To see how simple it is you can check the test application below.


MainForm.Designer.cs

namespace TestApp
{
    partial class MainForm
    {
        /// <summary>
        /// Required designer variable.
        /// </summary>
        private System.ComponentModel.IContainer components = null;

        /// <summary>
        /// Clean up any resources being used.
        /// </summary>
        /// <param name="disposing">true if managed resources should be disposed; otherwise, false.</param>
        protected override void Dispose(bool disposing)
        {
            if (disposing && (components != null))
            {
                components.Dispose();
            }
            base.Dispose(disposing);
        }

        #region Windows Form Designer generated code

        /// <summary>
        /// Required method for Designer support - do not modify
        /// the contents of this method with the code editor.
        /// </summary>
        private void InitializeComponent()
        {
            this.btnRun = new System.Windows.Forms.Button();
            this.rtxtOutput = new System.Windows.Forms.RichTextBox();
            this.SuspendLayout();
            // 
            // btnRun
            // 
            this.btnRun.Location = new System.Drawing.Point(86, 312);
            this.btnRun.Name = "btnRun";
            this.btnRun.Size = new System.Drawing.Size(149, 33);
            this.btnRun.TabIndex = 0;
            this.btnRun.Text = "Get All Prizes Combinations";
            this.btnRun.UseVisualStyleBackColor = true;
            this.btnRun.Click += new System.EventHandler(this.btnRun_Click);
            // 
            // rtxtOutput
            // 
            this.rtxtOutput.Location = new System.Drawing.Point(12, 2);
            this.rtxtOutput.Name = "rtxtOutput";
            this.rtxtOutput.Size = new System.Drawing.Size(299, 304);
            this.rtxtOutput.TabIndex = 5;
            this.rtxtOutput.Text = "";
            // 
            // MainForm
            // 
            this.AutoScaleDimensions = new System.Drawing.SizeF(6F, 13F);
            this.AutoScaleMode = System.Windows.Forms.AutoScaleMode.Font;
            this.ClientSize = new System.Drawing.Size(321, 347);
            this.Controls.Add(this.rtxtOutput);
            this.Controls.Add(this.btnRun);
            this.Name = "MainForm";
            this.Text = "Test Application";
            this.ResumeLayout(false);

        }

        #endregion

        private System.Windows.Forms.Button btnRun;
        private System.Windows.Forms.RichTextBox rtxtOutput;
    }
}

MainForm.cs

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Windows.Forms;
using System.IO;
using DevelopmentSimplyPut.CommonUtilities;
using System.Globalization;

namespace TestApp
{
    public partial class MainForm : Form
    {
        public MainForm()
        {
            InitializeComponent();
        }

        private void btnRun_Click(object sender, EventArgs e)
        {
            rtxtOutput.Text = string.Empty;

            string[] colors = new string[2] { "White", "Black" };
            string[] brands = new string[2] { "Nokia", "Samsung" };
            string[] os = new string[2] { "Symbian", "Android" };

            Int64[] attributesSizes = new Int64[3];
            attributesSizes[0] = colors.Length;
            attributesSizes[1] = brands.Length;
            attributesSizes[2] = os.Length;

            PossibilitiesCube container = new PossibilitiesCube(2, attributesSizes);
            container.AttributesCombinationValidator = new Func<Int64[], bool>
                    (
                        delegate(Int64[] attributesCombination)
                        {
                            bool result = true;
                            //filter out if the brand is "Samsung" and the os is "Symbian"
                            if (attributesCombination[1] == 1 && attributesCombination[2] == 0)
                            {
                                result = false;
                            }
                            return result;
                        }
                    );

            container.InstancesCombinationValidator = new Func<Int64[], bool>
                    (
                        delegate(Int64[] instanceCombination)
                        {
                            bool result = true;
                            //filter out if both mobile phones are identical
                            if (instanceCombination[0] == instanceCombination[1])
                            {
                                result = false;
                            }
                            return result;
                        }
                    );

            container.BuildPossibilitiesMatrix();

            for (Int64 i = 0; i <= container.InstancesCombinationsMaxRowIndex; i++)
            {
                if (container.CombinationsExist)
                {
                    for (Int64 k = 0; k <= container.InstancesCombinationsMaxColumnIndex; k++)
                    {
                        string color1 = colors[container[i, k, 0]];
                        string brand1 = brands[container[i, k, 1]];
                        string os1 = os[container[i, k, 2]];
                        rtxtOutput.Text += string.Format(CultureInfo.InvariantCulture, "[{0},{1},{2}]", color1, brand1, os1) + ((k != container.InstancesCombinationsMaxColumnIndex) ? "\t" : string.Empty);
                    }

                    rtxtOutput.Text += Environment.NewLine;
                }   
            }

            MessageBox.Show(string.Format(CultureInfo.InvariantCulture, "{0} prize combinations are found.", container.InstancesCombinationsMaxRowIndex + 1));
        }
    }
}

So, after using the library to calculate all possibilities of the problem described above then running the test application, we will get the results as in the image below.

Notes:
Please keep in mind that if the number of attributes and instances are too big this may cause an arithmetic overflow.

[Update] This library is already used on Application To Generate Combined Images Of All Image-Categories Possible Combinations


That's it. You can download the code from here


Hope you find this library useful.
Goodbye.

Read More

How To Copy SQL Hierarchical Data At Run-time While Keeping Valid Internal References And Self Joins

Sometimes when you deal with hierarchical data structures you may need to perform internal copy operations. To imagine what I mean, you can keep up with the scenario illustrated below.

You have a "Departments" table which include all departments in your system. Each department should have a parent department except for the top department which has no parent.

Now, assume that at some point in your system you need to make duplicates of the existing departments and this should happen automatically at certain condition or at certain action triggered by system user. So, you need to write a stored procedure which will copy the existing departments in the "Departments" table and insert them in the same table.

So, you may think that it is just a simple INSERT-SELECT statement operating on the same table; "Departments" table. This will leads you to the result as in the image below.

Now, you should have a look on this image and re-think what you did, is this the result you wish to achieve?
If you don't know or you still think this is the right result, you can have a look on the image below.

As you see in the image above, the newly inserted departments are messed up regarding their parent departments IDs. This is because while copying the old departments and inserting the new ones you didn't calculate the new IDs of the parent departments so now each department has a parent ID referencing the old department not the appropriate newly created one. This is so wrong.

To understand what I mean, you can have a look on the image below.

As you can see the department which had ID equals to "1" should now have ID equals to "5". Also, the department which had ID equals to "2" should now have ID equals to 6" and so on........

So, the valid result you wish to achieve is as in the image below.

So, how to reach this result? This is the main question this article is trying to answer.

Steps

1. Declare a table variable in which we will keep the IDs mapping. Each record in this table will hold the old copied ID and its corresponding newly inserted ID. This way anytime we need to map an old ID to its new one we can use this table as a reference
2. Copy and insert departments one by one and for each insert you just copy the "ParentID" column value as it is and we will deal with it later to be updated with the right value. Also, for each insert, insert a record in the IDs mapping table to hold the old and new IDs
3. Update the "ParentID" column for the newly inserted departments with the new IDs depending on the IDs mapping table which now should be populated with IDs pairs

Now, it is the time for some code.

-- Variable to hold the ID of the department to be copied; the old department ID
DECLARE @OldDeptID INT

-- Variable to hold the ID of the newly copied department; the new department ID
DECLARE @NewDeptID INT

-- A table to hold the departments to be copied from the "Departments" table
-- The idx column is an identity column
DECLARE @DepartmentsToCopy TABLE (idx INT IDENTITY(1,1), ID INT, Name VARCHAR(100), ParentID INT)

-- A table to map each old copied ID to its new inserted ID
DECLARE @IdsMapping TABLE(Old_Id int , New_Id int)

-- A counter to be used in a loop
DECLARE @counter int
SET @counter = 1

-- Inserting the departments to be copied into the @DepartmentsToCopy table
-- Here we selected all records without any filtering but this can be modified
-- according to your business needs
INSERT INTO @DepartmentsToCopy
(
 ID
 , Name
 , ParentID
)
SELECT ID
, Name
, ParentID
FROM Departments

-- Looping on each department record in the @DepartmentsToCopy table to perform
-- the required actions on each record one by one
WHILE @counter <= (select max(idx) from @DepartmentsToCopy)
BEGIN
 -- Inserting a copy of the current department record in the "Departments" table
 -- but with adding the word "New" at the end of the "Name" column
 INSERT INTO Departments
 (
  ID
  , Name
  , ParentID
 )   
 SELECT TOP 1 ID
 , Name + 'New'
 , ParentID
 FROM @DepartmentsToCopy
 WHERE idx = @counter
 
 -- Setting the value of @NewDeptID with the scope identity
 -- in order to hold the ID of the newly inserted department record
 SET @NewDeptID = SCOPE_IDENTITY()
 
 -- Setting the value of @OldDeptID with the old copied ID
 SELECT TOP 1
 @OldDeptID = ID
 FROM @DepartmentsToCopy
 WHERE idx = @counter
 
 -- Inserting a record into the @IdsMapping table to hold the IDs mapping
 -- where the old id is @OldDeptID and the new one is @NewDeptID
 INSERT INTO @IdsMapping
 (
    Old_Id
  , New_Id
 )
 VALUES(@OldDeptID, @NewDeptID)
 
 -- Incrementing the counter to work on the next department record
 SET @counter = @counter + 1
END

-- Updating the ParentID column of the newly inserted departments
-- to match the new IDs using the @IdsMapping table which hold the IDs mapping
UPDATE Departments
SET ParentID = map.New_Id
FROM Departments AS Dept
INNER JOIN @IdsMapping AS newOnly
ON Dept.ID = newOnly.New_Id
INNER JOIN @IdsMapping AS map
ON Dept.ParentID = map.Old_Id

That's it. Hope you will find this helpful someday.

Read More

How To Transform Unsorted Flat Hierarchical Data Structures Into Nested Parent-Child Or Tree Form Objects

Assume that you have hierarchical data structure presented into an SQL database table as in the image below.

As you can see each employee in the "Employees" table above can have a Manager which is an employee himself. In this case when the employee "Tarek" has "ManagerID" whose ID = 1, then "Tarek" has "Ahmed" as his manager. While "Ahmed" doesn't have a manager as he is the top manager.

This leads us to visualize the whole structure into parent-child relation as in the image below.

So, as we can see the data we can get from the "Employees" table is somehow flat because each data row will be represented by an "Employee" entity so at the end we can have a list of employees each preserves the ID of his manager as in the "Employee" entity below.

Employee.cs

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;

namespace DevelopmentSimplyPut.HierarchicalObjectsManagements.Entities
{
    public class Employee
    {
        public int ID { set; get; }
        public string Name { set; get; }
        public int? ManagerID { set; get; }

        public Employee() { }

        public Employee(int id, string name, int? managerID)
        {
            ID = id;
            Name = name;
            ManagerID = managerID;
        }
    }
}

Unfortunately this is not always enough as sometimes we find ourselves in a need to represent this data into a more structured form so that we can bind it with a tree control or whatever. So, we need to write some code to transform this unsorted flat hierarchical data structure into a parent-child or tree form.

To do so, let's first build an entity which will represent our parent-child or tree form to be used later. This leads us to the "EmployeeTreeNode" entity.

EmployeeTreeNode.cs

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;

namespace DevelopmentSimplyPut.HierarchicalObjectsManagements.Entities
{
    public class EmployeeTreeNode
    {
        public Employee Employee { set; get; }
        public bool IsProcessed { set; get; }
        public int Level { set; get; }

        private List<EmployeeTreeNode> childNodes;
        public List<EmployeeTreeNode> ChildNodes
        {
            get { return childNodes; }
        }

        public EmployeeTreeNode()
        {
            Level = 0;
            childNodes = new List<EmployeeTreeNode>();
        }

        public EmployeeTreeNode(Employee employee, bool isProcessed) : this()
        {
            Level = 0;
            Employee = employee;
            IsProcessed = isProcessed;
        }
    }
}

Now, we need to write the code which will do the transformation part. This is the code where the magic happens.

Utilities.cs

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using DevelopmentSimplyPut.HierarchicalObjectsManagements.Entities;

namespace DevelopmentSimplyPut.HierarchicalObjectsManagements.Utilities
{
    public static class Utilities
    {
        public static EmployeeTreeNode GetEmployeeTreeNode(List<Employee> employees)
        {
            EmployeeTreeNode result = new EmployeeTreeNode();
            result.IsProcessed = false;

            List<EmployeeTreeNode> nodes = new List<EmployeeTreeNode>();
            foreach (Employee emp in employees)
            {
                nodes.Add(new EmployeeTreeNode(emp, false));
            }

            foreach (EmployeeTreeNode empNode in nodes)
            {
                if (empNode.IsProcessed)
                {
                    continue;
                }
                else
                {
                    if (null == empNode.Employee.ManagerID)
                    {
                        result = empNode;
                        empNode.IsProcessed = true;
                        empNode.Level = 0;
                    }
                    else
                    {
                        ProcessNode(empNode, nodes);
                    }
                }
            }

            if (result.ChildNodes.Count == 0)
            {
                result.ChildNodes.AddRange(nodes);
            }

            return result;
        }

        private static void ProcessNode(EmployeeTreeNode node, List<EmployeeTreeNode> nodes)
        {
            EmployeeTreeNode parentNode = nodes.DefaultIfEmpty(null).FirstOrDefault(n => n.Employee.ID == node.Employee.ManagerID);
            if (null != parentNode)
            {
                if (!parentNode.IsProcessed)
                {
                    ProcessNode(parentNode, nodes);
                }

                node.IsProcessed = true;
                node.Level = parentNode.Level + 1;
                node.Parent = parentNode;
                parentNode.ChildNodes.Add(node);
            }
            else
            {
                node.IsProcessed = true;
                node.Level = 0;
                node.Parent = null;
            }
        }

        public static string Repeat(this string source, int numOfTimes)
        {
            string result = source;

            if (numOfTimes > 0)
            {
                for (int i = 0; i < numOfTimes - 1; i++)
                {
                    result += source;
                }
            }
            else
            {
                result = string.Empty;
            }

            return result;
        }
    }
}

Now you can use the code above to get your parent-child or tree form from the unsorted flat hierarchical data structure. To validate the code above, here is a demo windows forms application which you can use.

Form1.Designer.cs

namespace HierarchicalObjectsManagements
{
    partial class Form1
    {
        /// <summary>
        /// Required designer variable.
        /// </summary>
        private System.ComponentModel.IContainer components = null;

        /// <summary>
        /// Clean up any resources being used.
        /// </summary>
        /// <param name="disposing">true if managed resources should be disposed; otherwise, false.</param>
        protected override void Dispose(bool disposing)
        {
            if (disposing && (components != null))
            {
                components.Dispose();
            }
            base.Dispose(disposing);
        }

        #region Windows Form Designer generated code

        /// <summary>
        /// Required method for Designer support - do not modify
        /// the contents of this method with the code editor.
        /// </summary>
        private void InitializeComponent()
        {
            this.btn_BuildTree = new System.Windows.Forms.Button();
            this.lst_Employees = new System.Windows.Forms.ListBox();
            this.SuspendLayout();
            // 
            // btn_BuildTree
            // 
            this.btn_BuildTree.Location = new System.Drawing.Point(181, 165);
            this.btn_BuildTree.Name = "btn_BuildTree";
            this.btn_BuildTree.Size = new System.Drawing.Size(75, 23);
            this.btn_BuildTree.TabIndex = 0;
            this.btn_BuildTree.Text = "Build Tree";
            this.btn_BuildTree.UseVisualStyleBackColor = true;
            this.btn_BuildTree.Click += new System.EventHandler(this.btn_BuildTree_Click);
            // 
            // lst_Employees
            // 
            this.lst_Employees.FormattingEnabled = true;
            this.lst_Employees.Location = new System.Drawing.Point(12, 12);
            this.lst_Employees.Name = "lst_Employees";
            this.lst_Employees.Size = new System.Drawing.Size(244, 147);
            this.lst_Employees.TabIndex = 1;
            // 
            // Form1
            // 
            this.AutoScaleDimensions = new System.Drawing.SizeF(6F, 13F);
            this.AutoScaleMode = System.Windows.Forms.AutoScaleMode.Font;
            this.ClientSize = new System.Drawing.Size(268, 193);
            this.Controls.Add(this.lst_Employees);
            this.Controls.Add(this.btn_BuildTree);
            this.Name = "Form1";
            this.Text = "Hierarchical Objects Management";
            this.ResumeLayout(false);

        }

        #endregion

        private System.Windows.Forms.Button btn_BuildTree;
        private System.Windows.Forms.ListBox lst_Employees;
    }
}

Form1.cs

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Windows.Forms;
using DevelopmentSimplyPut.HierarchicalObjectsManagements.Entities;
using DevelopmentSimplyPut.HierarchicalObjectsManagements.Utilities;

namespace HierarchicalObjectsManagements
{
    public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();
        }

        private void btn_BuildTree_Click(object sender, EventArgs e)
        {
            lst_Employees.Items.Clear();

            List<Employee> employees = new List<Employee>();
            employees.Add(new Employee(4, "Saleh", 2));
            employees.Add(new Employee(1, "Ahmed", null));
            employees.Add(new Employee(5, "Selim", 4));
            employees.Add(new Employee(2, "Tarek", 1));
            employees.Add(new Employee(6, "Mohamed", 2));
            employees.Add(new Employee(3, "Hasan", 1));

            EmployeeTreeNode employeeTreeTopNode = Utilities.GetEmployeeTreeNode(employees);

            BuildTree(employeeTreeTopNode);
            MessageBox.Show("Done");
        }

        public void BuildTree(EmployeeTreeNode node)
        {
            lst_Employees.Items.Add("-".Repeat(node.Level) + node.Employee.Name);
            foreach (EmployeeTreeNode childNode in node.ChildNodes)
            {
                BuildTree(childNode);
            }
        }
    }
}

After running the windows form application, you will get the result as in the image below.

That's it. This is just a proof of concept but you can tweak it to satisfy your specific business and needs. I hope this helps you someday :)

You can download the code from here


Good Bye.

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