Remove duplicate records from a table

This code sample shows how to identify and remove duplicate records from a dataset/datatable.Following Code will take inputs datatable and column name wherein we need to find duplicates items and remove

public DataTable RemoveDuplicateRows(DataTable dTable, string colName)
{

Hashtable hTable = new Hashtable();

ArrayList duplicateList = new ArrayList();
//Add list of all the unique item value to hashtable, which stores combination of key, value pair.
//And add duplicate item value in arraylist.

foreach (DataRow drow in dTable.Rows)
{

if (hTable.Contains(drow[colName]))
duplicateList.Add(drow);
else
hTable.Add(drow[colName], string.Empty);
}

//Removing a list of duplicate items from datatable.

foreach (DataRow dRow in duplicateList)
dTable.Rows.Remove(dRow);
//Datatable which contains unique records will be return as output.
return dTable;
}

Example showing how to use above method:

protected void Button1_Click(object sender, EventArgs e)
{
string strConn = ConfigurationManager.ConnectionStrings["ConnectionString"].ToString(); SqlConnection conn = new SqlConnection(strConn);

SqlDataAdapter da = new SqlDataAdapter("select * from emp", conn);
DataSet ds = new DataSet();

da.Fill(ds, "Emp");

// Filling a employee table
DataTable dt = ds.Tables["Emp"];
dt = RemoveDuplicateRows(dt, "empname");
GridView1.DataSource = ds.Tables["Emp"].DefaultView;
GridView1.DataBind();
}