Bind DropDownList based on another inside GridView in ASP.Net

protected void drpdwnbranch_SelectedIndexChanged(object sender, EventArgs e)
    {
        if (drpdwnbranch.SelectedItem.ToString() != "--Select Branch--")
        {
            DataSet ds1 = sql.getds("Select department.department_name,branch_department.department_id from branch_department join department on department.department_id=branch_department.department_id where branch_id='" + drpdwnbranch.SelectedValue.ToString() + "'");
            drpdwndepartment.DataTextField = "department_name";
            drpdwndepartment.DataValueField = "department_id";
            drpdwndepartment.DataSource = ds1;
            drpdwndepartment.DataBind();
            drpdwndepartment.Items.Insert(0, new ListItem("--Select Department--", "0"));
}
}

Hi Richa,

Refer below article.

AJAX Cascading DropDownList with Database in GridView Example in ASP.Net using C# VB.Net