Dynamically add DropDownList in TemplateField Columns in ASP.Net GridView using C# and VB.Net

Hi AshiWar,

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

Database

I have made use of the following table Customers with the schema as follows.

I have already inserted few records in the table.

You can download the database table SQL by clicking the download link below.

Download SQL file

HTML

<asp:GridView ID="GridView1" runat="server" AutoGenerateColumns="false" OnRowDataBound="OnRowDataBound">
</asp:GridView>

Namespaces

C#

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

VB.Net

Imports System.Configuration
Imports System.Data
Imports System.Data.SqlClient

Code

C#

protected void Page_Load(object sender, EventArgs e)
{
    if (!this.IsPostBack)
    {
        BoundField bfield = new BoundField();
        bfield.HeaderText = "Id";
        bfield.DataField = "CustomerId";
        GridView1.Columns.Add(bfield);

        TemplateField tfield = new TemplateField();
        tfield.HeaderText = "Name";
        GridView1.Columns.Add(tfield);

        tfield = new TemplateField();
        tfield.HeaderText = "Country";
        GridView1.Columns.Add(tfield);

        tfield = new TemplateField();
        tfield.HeaderText = "View";
        GridView1.Columns.Add(tfield);
    }
    this.BindGrid();
}

private void BindGrid()
{
    GridView1.DataSource = GetData();
    GridView1.DataBind();
}

protected void OnRowDataBound(object sender, GridViewRowEventArgs e)
{
    if (e.Row.RowType == DataControlRowType.DataRow)
    {
        TextBox txtName = new TextBox();
        txtName.ID = "txtName";
        txtName.Text = (e.Row.DataItem as DataRowView).Row["Name"].ToString();
        e.Row.Cells[1].Controls.Add(txtName);

        DropDownList ddlCountry = new DropDownList();
        ddlCountry.ID = "ddlCountry";
        ddlCountry.DataSource = GetData();
        ddlCountry.DataTextField = GetData().Columns[1].ColumnName;
        ddlCountry.DataValueField = GetData().Columns[0].ColumnName;
        ddlCountry.DataBind();
        string country = (e.Row.DataItem as DataRowView).Row["Country"].ToString();
        ddlCountry.Items.FindByText(country).Selected = true;
        e.Row.Cells[2].Controls.Add(ddlCountry);

        LinkButton lnkView = new LinkButton();
        lnkView.ID = "lnkView";
        lnkView.Text = "View";
        lnkView.Click += ViewDetails;
        lnkView.CommandArgument = (e.Row.DataItem as DataRowView).Row["CustomerId"].ToString();
        e.Row.Cells[3].Controls.Add(lnkView);
    }
}

private DataTable GetData()
{
    string conString = ConfigurationManager.ConnectionStrings["constr"].ConnectionString;
    string query = "SELECT CustomerId,Country,Name FROM Customers";
    SqlCommand cmd = new SqlCommand(query);
    using (SqlConnection con = new SqlConnection(conString))
    {
        using (SqlDataAdapter sda = new SqlDataAdapter())
        {
            cmd.Connection = con;
            sda.SelectCommand = cmd;
            using (DataTable dt = new DataTable())
            {
                sda.Fill(dt);
                return dt;
            }
        }
    }
}

protected void ViewDetails(object sender, EventArgs e)
{
    LinkButton lnkView = (sender as LinkButton);
    GridViewRow row = (lnkView.NamingContainer as GridViewRow);
    string id = lnkView.CommandArgument;
    string name = (row.FindControl("txtName") as TextBox).Text;
    string country = (row.FindControl("ddlCountry") as DropDownList).SelectedItem.Text;
    ClientScript.RegisterStartupScript(this.GetType(), "alert", "alert('Id: " + id + "\\n\\rName: " + name + "\\n\\rCountry: " + country + "')", true);
}

VB.Net

Protected Sub Page_Load(ByVal sender As Object, ByVal e As EventArgs) Handles Me.Load
    If Not Me.IsPostBack Then
        Dim bfield As BoundField = New BoundField()
        bfield.HeaderText = "Id"
        bfield.DataField = "CustomerId"
        GridView1.Columns.Add(bfield)

        Dim tfield As TemplateField = New TemplateField()
        tfield.HeaderText = "Name"
        GridView1.Columns.Add(tfield)

        tfield = New TemplateField()
        tfield.HeaderText = "Country"
        GridView1.Columns.Add(tfield)

        tfield = New TemplateField()
        tfield.HeaderText = "View"
        GridView1.Columns.Add(tfield)
    End If
    Me.BindGrid()
End Sub

Private Sub BindGrid()
    GridView1.DataSource = GetData()
    GridView1.DataBind()
End Sub

Protected Sub OnRowDataBound(ByVal sender As Object, ByVal e As GridViewRowEventArgs)
    If e.Row.RowType = DataControlRowType.DataRow Then
        Dim txtName As TextBox = New TextBox()
        txtName.ID = "txtName"
        txtName.Text = (TryCast(e.Row.DataItem, DataRowView)).Row("Name").ToString()
        e.Row.Cells(1).Controls.Add(txtName)

        Dim ddlCountry As DropDownList = New DropDownList()
        ddlCountry.ID = "ddlCountry"
        ddlCountry.DataSource = GetData()
        ddlCountry.DataTextField = GetData().Columns(1).ColumnName
        ddlCountry.DataValueField = GetData().Columns(0).ColumnName
        ddlCountry.DataBind()
        Dim country As String = (TryCast(e.Row.DataItem, DataRowView)).Row("Country").ToString()
        ddlCountry.Items.FindByText(country).Selected = True
        e.Row.Cells(2).Controls.Add(ddlCountry)

        Dim lnkView As LinkButton = New LinkButton()
        lnkView.ID = "lnkView"
        lnkView.Text = "View"
        AddHandler lnkView.Click, AddressOf ViewDetails
        lnkView.CommandArgument = (TryCast(e.Row.DataItem, DataRowView)).Row("CustomerId").ToString()
        e.Row.Cells(3).Controls.Add(lnkView)
    End If
End Sub

Private Function GetData() As DataTable
    Dim conString As String = ConfigurationManager.ConnectionStrings("constr").ConnectionString
    Dim query As String = "SELECT CustomerId,Country,Name FROM Customers"
    Dim cmd As SqlCommand = New SqlCommand(query)
    Using con As SqlConnection = New SqlConnection(conString)
        Using sda As SqlDataAdapter = New SqlDataAdapter()
            cmd.Connection = con
            sda.SelectCommand = cmd
            Using dt As DataTable = New DataTable()
                sda.Fill(dt)
                Return dt
            End Using
        End Using
    End Using
End Function

Protected Sub ViewDetails(ByVal sender As Object, ByVal e As EventArgs)
    Dim lnkView As LinkButton = (TryCast(sender, LinkButton))
    Dim row As GridViewRow = (TryCast(lnkView.NamingContainer, GridViewRow))
    Dim id As String = lnkView.CommandArgument
    Dim name As String = (TryCast(row.FindControl("txtName"), TextBox)).Text
    Dim country As String = (TryCast(row.FindControl("ddlCountry"), DropDownList)).SelectedItem.Text
    ClientScript.RegisterStartupScript(Me.[GetType](), "alert", "alert('Id: " & id & "\n\rName: " & name & "\n\rCountry: " & country & "')", True)
End Sub

Screenshot