Merge Column header inside ASP.Net GridView using C# and VB.Net

Hi akhter,

Please refer below sample.

Database

For this example I have used of Northwind database that you can download using the link given below.

Download Northwind Database

HTML

<asp:GridView ID="gvDetails" runat="server" AutoGenerateColumns="false" 
    OnDataBound="gvDetails_DataBound">
    <Columns>
        <asp:BoundField HeaderText="CompanyName" DataField="ContactName" />
        <asp:BoundField HeaderText="ContactName" DataField="ContactName" />
        <asp:BoundField HeaderText="Address" DataField="Address" />
        <asp:BoundField HeaderText="City" DataField="City" />
    </Columns>
</asp:GridView>

Namespaces

C#

using System.Configuration;
using System.Data.SqlClient;

VB.Net

Imports System.Configuration
Imports System.Data.SqlClient

Code

C#

protected void Page_Load(object sender, EventArgs e)
{
    if (!this.IsPostBack)
    {
        this.GridViewBind();
    }
}

private void GridViewBind()
{
    string conString = ConfigurationManager.ConnectionStrings["constr"].ConnectionString;
    using (SqlConnection con = new SqlConnection(conString))
    {
        using (SqlCommand cmd = new SqlCommand("SELECT Top 10 CompanyName, ContactName, Address, City FROM Customers", con))
        {
            con.Open();
            gvDetails.DataSource = cmd.ExecuteReader();
            gvDetails.DataBind();
            con.Close();
        }
    }
}

protected void gvDetails_DataBound(object sender, EventArgs e)
{
    GridViewRow row = new GridViewRow(0, 0, DataControlRowType.Header, DataControlRowState.Normal);
    TableHeaderCell cell = new TableHeaderCell();
    cell.Text = "Name";
    cell.ColumnSpan = 2;
    row.Controls.Add(cell);
    cell = new TableHeaderCell();
    cell.ColumnSpan = 2;
    cell.Text = "Address";
    row.Controls.Add(cell);        
    gvDetails.HeaderRow.Parent.Controls.AddAt(0, row);
}

VB.Net

Protected Sub Page_Load(ByVal sender As Object, ByVal e As EventArgs) Handles Me.Load
    If Not Me.IsPostBack Then
        Me.GridViewBind()
    End If
End Sub

Private Sub GridViewBind()
    Dim conString As String = ConfigurationManager.ConnectionStrings("constr").ConnectionString
    Using con As SqlConnection = New SqlConnection(conString)
        Using cmd As SqlCommand = New SqlCommand("SELECT Top 10 CompanyName, ContactName, Address, City FROM Customers", con)
            con.Open()
            gvDetails.DataSource = cmd.ExecuteReader()
            gvDetails.DataBind()
            con.Close()
        End Using
    End Using
End Sub

Protected Sub gvDetails_DataBound(ByVal sender As Object, ByVal e As EventArgs)
    Dim row As GridViewRow = New GridViewRow(0, 0, DataControlRowType.Header, DataControlRowState.Normal)
    Dim cell As TableHeaderCell = New TableHeaderCell()
    cell.Text = "Name"
    cell.ColumnSpan = 2
    row.Controls.Add(cell)
    cell = New TableHeaderCell()
    cell.ColumnSpan = 2
    cell.Text = "Address"
    row.Controls.Add(cell)
    gvDetails.HeaderRow.Parent.Controls.AddAt(0, row)
End Sub

Screenshot

Reference: GridView with Multiple Headers in ASP.Net