Remove duplicate rows from a DataTable

--------- Demo Removing Duplicate rows in a DataTable ----------------

using System;

using System.Data;

using System.Collections;

 

namespace Demo_DataTableRemoveDupRows

{

class Class1

{

[STAThread]

static void Main(string[] args)

{

 

// create an example datatable with duplicate rows

DataTable tbl = new DataTable();

 

tbl.Columns.Add("ColumnA");

tbl.Columns.Add("ColumnB");

tbl.Columns.Add("ColumnC");

for(int i = 0; i<10; i++)

{

DataRow nr = tbl.NewRow();

nr["ColumnA"] = "A" + i.ToString();

nr["ColumnB"] = "B" + i.ToString();

nr["ColumnC"] = "C" + i.ToString();

tbl.Rows.Add(nr);

// duplicate

nr = tbl.NewRow();

nr["ColumnA"] = "A" + i.ToString();

nr["ColumnB"] = "B" + i.ToString();

nr["ColumnC"] = "C" + i.ToString();

tbl.Rows.Add(nr);

}

 

PrintRows(tbl); // show table with duplicates

 

//Create an array of DataColumns to compare

//If these columns all match we consider the

                  //rows duplicate.

DataColumn[] keyColumns =

                              new DataColumn[]{tbl.Columns["ColumnA"],

                                               tbl.Columns["ColumnA"]};

 

//remove the duplicates

RemoveDuplicates(tbl, keyColumns);

 

 

PrintRows(tbl); // show table again

Console.ReadLine(); // pause to view output

 

}

/// <summary>

/// Removes duplicate rows from given DataTable

/// </summary>

/// <param name="tbl">Table to scan for duplicate rows</param>

/// <param name="KeyColumns">An array of DataColumns

///   containing the columns to match for duplicates</param>

private static void RemoveDuplicates(DataTable tbl,

DataColumn[] keyColumns)

{

int rowNdx = 0;

while(rowNdx < tbl.Rows.Count-1)

{

DataRow[] dups = FindDups(tbl, rowNdx, keyColumns);

if(dups.Length>0)

{

foreach(DataRow dup in dups)

{

tbl.Rows.Remove(dup);

}

}

else

{

rowNdx++;

}

}

}

 

private static DataRow[] FindDups(DataTable tbl,

int sourceNdx,

DataColumn[] keyColumns)

{

ArrayList retVal = new ArrayList();

 

DataRow sourceRow = tbl.Rows[sourceNdx];

for(int i=sourceNdx + 1; i<tbl.Rows.Count; i++)

{

DataRow targetRow = tbl.Rows[i];

if(IsDup(sourceRow, targetRow, keyColumns))

{

retVal.Add(targetRow);

}

}

return (DataRow[]) retVal.ToArray(typeof(DataRow));

}

 

private static bool IsDup(DataRow sourceRow,

DataRow targetRow,

DataColumn[] keyColumns)

{

bool retVal = true;

foreach(DataColumn column in keyColumns)

{

retVal = retVal && sourceRow[column].Equals(targetRow[column]);

if(!retVal) break;

}

return retVal;

}

 

private static void PrintRows(DataTable tbl)

{

for(int i=0; i<tbl.Rows.Count; i++)

{

Console.WriteLine("row: {0}, ColumnA: {1}, ColumnB: {2}", i, tbl.Rows[i]["ColumnA"], tbl.Rows[i]["ColumnB"]);

}

 

}

}

}

--------- End Demo Code ----------------