Show (Display) NULL when ASP.Net GridView Cell value is Empty using C# and VB.Net

Hi HarisAgha,

Refer below sample.

HTML

<asp:GridView ID="GridView1" runat="server" AutoGenerateColumns="false" OnRowDataBound="GridView1_RowDataBound">
    <Columns>
        <asp:BoundField DataField="CustomerId" HeaderText="CustomerId" />
        <asp:BoundField DataField="Name" HeaderText="Name" />
        <asp:TemplateField HeaderText="Country">
            <ItemTemplate>
                <asp:Label Text='<%#Eval("Country") %>' ID="lblCountry" runat="server" />
            </ItemTemplate>
        </asp:TemplateField>
    </Columns>
</asp:GridView>

Namespaces

C#

using System.Data;

VB.Net

Imports System.Drawing
Imports System.Data

Code

C#

protected void Page_Load(object sender, EventArgs e)
{
    if (!this.IsPostBack)
    {
        DataTable dt = new DataTable();
        dt.Columns.AddRange(new DataColumn[3] { new DataColumn("CustomerId", typeof(int)),
                        new DataColumn("Name", typeof(string)),
                        new DataColumn("Country",typeof(string)) });
        dt.Rows.Add(1, "John Hammond", "United States");
        dt.Rows.Add(2, "Mudassar Khan", "India");
        dt.Rows.Add(3, "Suzanne Mathews", "");
        dt.Rows.Add(4, "", "Russia");
        GridView1.DataSource = dt;
        GridView1.DataBind();
    }
}

protected void GridView1_RowDataBound(object sender, GridViewRowEventArgs e)
{
    if (e.Row.RowType == DataControlRowType.DataRow)
    {
        for (int i = 0; i < e.Row.Cells.Count; i++)
        {
            foreach (Control control in e.Row.Cells[i].Controls)
            {
                if (control.GetType().Name == "Label")
                {
                    if (string.IsNullOrEmpty((control as Label).Text))
                    {
                        e.Row.Cells[i].Text = "NULL";
                    }
                }
            }
            if (e.Row.Cells[i].Text == "&nbsp;")
            {
                e.Row.Cells[i].Text = "NULL";
            }
        }
    }
}

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 DataTable = New DataTable()
        dt.Columns.AddRange(New DataColumn(2) {New DataColumn("CustomerId", GetType(Integer)), New DataColumn("Name", GetType(String)), New DataColumn("Country", GetType(String))})
        dt.Rows.Add(1, "John Hammond", "United States")
        dt.Rows.Add(2, "Mudassar Khan", "India")
        dt.Rows.Add(3, "Suzanne Mathews", "")
        dt.Rows.Add(4, "", "Russia")
        GridView1.DataSource = dt
        GridView1.DataBind()
    End If
End Sub

Protected Sub GridView1_RowDataBound(ByVal sender As Object, ByVal e As GridViewRowEventArgs)
    If e.Row.RowType = DataControlRowType.DataRow Then
        For i As Integer = 0 To e.Row.Cells.Count - 1
            For Each control As Control In e.Row.Cells(i).Controls
                If control.[GetType]().Name = "Label" Then

                    If String.IsNullOrEmpty((TryCast(control, Label)).Text) Then
                        e.Row.Cells(i).Text = "NULL"
                    End If
                End If
            Next
            If e.Row.Cells(i).Text = " " Then
                e.Row.Cells(i).Text = "NULL"
            End If
        Next
    End If
End Sub

Screenshot