How to remove duplicate records from DataTable using C# and VB.Net in ASP.Net

Hi abraham197,

I have created sample code which full-fill your requirement. So please refer the below code.

HTML

<div>
    <asp:GridView ID="gvRecords" AutoGenerateColumns="true" runat="server" />
</div>

C#

protected void Page_Load(object sender, EventArgs e)
{
    if (!IsPostBack)
    {
        DataTable dt = new DataTable();
        dt.Columns.Add("CustomerId");
        dt.Columns.Add("Name");
        dt.Columns.Add("Country");
        dt.Rows.Add("1", "Mudassar Khan", "India");
        dt.Rows.Add("2", "Maria", "Austria");
        dt.Rows.Add("3", "Ana Trujillo", "UK");
        dt.Rows.Add("4", "Thomas Hardy ", "Brazil");
        dt.Rows.Add("4", "Thomas Hardy ", "Brazil");
        dt.Rows.Add("5", "Christina Berglund", "Ireland");
        dt.Rows.Add("2", "Maria", "Austria");
        DataTable UniqueRecords = RemoveDuplicateRows(dt, "CustomerId");
        gvRecords.DataSource = UniqueRecords;
        gvRecords.DataBind();
    }
}

public DataTable RemoveDuplicateRows(DataTable table, string DistinctColumn)
{
    try
    {
        ArrayList UniqueRecords = new ArrayList();
        ArrayList DuplicateRecords = new ArrayList();
        foreach (DataRow dRow in table.Rows)
        {
            if (UniqueRecords.Contains(dRow[DistinctColumn]))
                DuplicateRecords.Add(dRow);
            else
                UniqueRecords.Add(dRow[DistinctColumn]);
        }

        foreach (DataRow dRow in DuplicateRecords)
        {
            table.Rows.Remove(dRow);
        }

        return table;
    }
    catch (Exception ex)
    {
        return null;
    }
}

Vb.Net

Protected Sub Page_Load(sender As Object, e As EventArgs) Handles Me.Load
	If Not IsPostBack Then
		Dim dt As New DataTable()
		dt.Columns.Add("CustomerId")
		dt.Columns.Add("Name")
		dt.Columns.Add("Country")
		dt.Rows.Add("1", "Mudassar Khan", "India")
		dt.Rows.Add("2", "Maria", "Austria")
		dt.Rows.Add("3", "Ana Trujillo", "UK")
		dt.Rows.Add("4", "Thomas Hardy ", "Brazil")
		dt.Rows.Add("4", "Thomas Hardy ", "Brazil")
		dt.Rows.Add("5", "Christina Berglund", "Ireland")
		dt.Rows.Add("2", "Maria", "Austria")
		Dim UniqueRecords As DataTable = RemoveDuplicateRows(dt, "CustomerId")
		gvRecords.DataSource = UniqueRecords
		gvRecords.DataBind()
	End If
End Sub

Public Function RemoveDuplicateRows(table As DataTable, DistinctColumn As String) As DataTable
	Try
		Dim UniqueRecords As New ArrayList()
		Dim DuplicateRecords As New ArrayList()
		For Each dRow As DataRow In table.Rows
			If UniqueRecords.Contains(dRow(DistinctColumn)) Then
				DuplicateRecords.Add(dRow)
			Else
				UniqueRecords.Add(dRow(DistinctColumn))
			End If
		Next

		For Each dRow As DataRow In DuplicateRecords
			table.Rows.Remove(dRow)
		Next

		Return table
	Catch ex As Exception
		Return Nothing
	End Try
End Function

 Output