Display GridView cell value in TextBox on Page Load in ASP.Net

Hi david.ee,

Please take reference the below code and correct your code.

Database

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

Download Northwind Database

HTML

<asp:GridView ID="gvCustomers" runat="server" AutoGenerateColumns="False">
    <Columns>
        <asp:TemplateField HeaderText="ContactName" Visible="False">
            <ItemTemplate>
                <asp:Label ID="lblContactName" runat="server" Text='<%# Eval("ContactName") %>'></asp:Label>
            </ItemTemplate>
        </asp:TemplateField>
        <asp:TemplateField HeaderText="CustomerID">
            <ItemTemplate>
                <asp:Label ID="lblCustomerID" runat="server" Text='<%# Eval("CustomerID") %>'></asp:Label>
            </ItemTemplate>
        </asp:TemplateField>
        <asp:TemplateField HeaderText="City">
            <ItemTemplate>
                <asp:Label ID="lblCity" runat="server" Text='<%# Eval("City") %>'></asp:Label>
            </ItemTemplate>
        </asp:TemplateField>
        <asp:TemplateField HeaderText="Country">
            <ItemTemplate>
                <asp:Label ID="lblCountry" runat="server" Text='<%# Eval("Country") %>'></asp:Label>
            </ItemTemplate>
        </asp:TemplateField>
    </Columns>
</asp:GridView>
<br />
<asp:TextBox ID="txtCustomerIds" runat="server" Width="300px"></asp:TextBox>

Namespaces

C#

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

VB.Net

Imports System.Data.SqlClient
Imports System.Data

Code

C#

protected void Page_Load(object sender, EventArgs e)
{
    if (!this.IsPostBack)
    {
        string constr = ConfigurationManager.ConnectionStrings["Constring"].ConnectionString;
        using (SqlConnection con = new SqlConnection(constr))
        {
            using (SqlCommand cmd = new SqlCommand("SELECT TOP 5 CustomerID,ContactName,City,Country FROM Customers", con))
            {
                using (SqlDataAdapter da = new SqlDataAdapter(cmd))
                {
                    using (DataTable dt = new DataTable())
                    {
                        da.Fill(dt);
                        this.gvCustomers.DataSource = dt;
                        this.gvCustomers.DataBind();

                        for (int i = 0; i < this.gvCustomers.Rows.Count; i++)
                        {
                            this.txtCustomerIds.Text += (this.gvCustomers.Rows[i].FindControl("lblCustomerID") as Label).Text + " ";
                        }
                    }
                }
            }
        }
    }
}

Vb.Net

Protected Sub Page_Load(ByVal sender As Object, ByVal e As EventArgs) Handles Me.Load
    If Not Me.IsPostBack Then
        Dim constr As String = ConfigurationManager.ConnectionStrings("Constring").ConnectionString
        Using con As SqlConnection = New SqlConnection(constr)

            Using cmd As SqlCommand = New SqlCommand("SELECT TOP 5 CustomerID,ContactName,City,Country FROM Customers", con)
                Using da As SqlDataAdapter = New SqlDataAdapter(cmd)
                    Using dt As DataTable = New DataTable()
                        da.Fill(dt)
                        Me.gvCustomers.DataSource = dt
                        Me.gvCustomers.DataBind()
                        For i As Integer = 0 To Me.gvCustomers.Rows.Count - 1
                            Me.txtCustomerIds.Text += (TryCast(Me.gvCustomers.Rows(i).FindControl("lblCustomerID"), Label)).Text & " "
                        Next
                    End Using
                End Using
            End Using
        End Using
    End If
End Sub

Screenshot