Duplicate row selection validation with CheckBox in ASP.Net GridView

Hi narasiman,

Check this example. Now please take its reference and correct your code.

HTML

<asp:GridView ID="GridView1" runat="server" AutoGenerateColumns="false">
    <Columns>
        <asp:TemplateField HeaderText="Selectdata">
            <ItemTemplate>
                <asp:CheckBox ID="chkSelect" runat="server" />
            </ItemTemplate>
        </asp:TemplateField>
        <asp:BoundField DataField="Slipno" HeaderText="Slipno" />
        <asp:BoundField DataField="Slipdate" HeaderText="Date" />
        <asp:BoundField DataField="Location" HeaderText="Location" />
        <asp:BoundField DataField="Section" HeaderText="Section" />
        <asp:BoundField DataField="Status" HeaderText="Status" />
    </Columns>
</asp:GridView>
<br />
<asp:Button Text="Save" runat="server" OnClick="Save" />

C#

protected void Page_Load(object sender, EventArgs e)
{
    if (!this.IsPostBack)
    {
        System.Data.DataTable dt = new System.Data.DataTable();
        dt.Columns.AddRange(new System.Data.DataColumn[] { 
                        new System.Data.DataColumn("Slipno", typeof(int)),
                        new System.Data.DataColumn("Slipdate", typeof(string)),
                        new System.Data.DataColumn("Location",typeof(int)),
                        new System.Data.DataColumn("Section",typeof(string)),
                        new System.Data.DataColumn("Status",typeof(string))});
        dt.Rows.Add(123, "28.05.2018", 1001, "Sordi", "New");
        dt.Rows.Add(123, "28.05.2018", 1002, "Ferke", "New");
        dt.Rows.Add(124, "28.05.2018", 1003, "Sordi", "New");
        dt.Rows.Add(124, "28.05.2018", 1004, "Sordi", "New");
        GridView1.DataSource = dt;
        GridView1.DataBind();
    }
}

protected void Save(object sender, EventArgs e)
{
    List<int> slipNos = new List<int>();
    foreach (GridViewRow row in GridView1.Rows)
    {
        if ((row.FindControl("chkSelect") as CheckBox).Checked)
        {
            slipNos.Add(Convert.ToInt32(row.Cells[1].Text.Trim()));
        }
    }
    List<int> duplicateSlips = slipNos.GroupBy(x => x).Where(g => g.Count() > 1).Select(y => y.Key).ToList();
    if (duplicateSlips.Count > 0)
    {
        ClientScript.RegisterClientScriptBlock(this.GetType(), "", "alert('For selected slipno " + string.Join(",", duplicateSlips) + " checkbox is selected.')", true);
    }
}

VB.Net

Protected Sub Page_Load(ByVal sender As Object, ByVal e As EventArgs) Handles Me.Load
    If Not Me.IsPostBack Then
        Dim dt As System.Data.DataTable = New System.Data.DataTable()
        dt.Columns.AddRange(New System.Data.DataColumn() {
                            New System.Data.DataColumn("Slipno", GetType(Integer)),
                            New System.Data.DataColumn("Slipdate", GetType(String)),
                            New System.Data.DataColumn("Location", GetType(Integer)),
                            New System.Data.DataColumn("Section", GetType(String)),
                            New System.Data.DataColumn("Status", GetType(String))})
        dt.Rows.Add(123, "28.05.2018", 1001, "Sordi", "New")
        dt.Rows.Add(123, "28.05.2018", 1002, "Ferke", "New")
        dt.Rows.Add(124, "28.05.2018", 1003, "Sordi", "New")
        dt.Rows.Add(124, "28.05.2018", 1004, "Sordi", "New")
        GridView1.DataSource = dt
        GridView1.DataBind()
    End If
End Sub

Protected Sub Save(ByVal sender As Object, ByVal e As EventArgs)
    Dim slipNos As List(Of Integer) = New List(Of Integer)()

    For Each row As GridViewRow In GridView1.Rows
        If (TryCast(row.FindControl("chkSelect"), CheckBox)).Checked Then
            slipNos.Add(Convert.ToInt32(row.Cells(1).Text.Trim()))
        End If
    Next

    Dim duplicateSlips As List(Of Integer) = slipNos.GroupBy(Function(x) x).Where(Function(g) g.Count() > 1).[Select](Function(y) y.Key).ToList()
    If duplicateSlips.Count > 0 Then
        ClientScript.RegisterClientScriptBlock(Me.[GetType](), "", "alert('For selected slipno " & String.Join(",", duplicateSlips) & " checkbox is selected.')", True)
    End If
End Sub

Screenshot