[Solved] Unable to cast object of type System.Web.UI.WebControls.ContentPlaceHolder to type System.Web.UI.WebControls.GridViewRow

Hi georgeacuster,

Your Image button is outside the gridview becouse of that you are getting the error.

You need to take the image button inside the gridview.

Please refer below sample.

HTML

<asp:GridView ID="GridView1" runat="server" AutoGenerateColumns="false" OnRowDataBound="OnRowDataBound">
    <Columns>
        <asp:TemplateField HeaderText="Select">
            <ItemTemplate>
                <asp:CheckBox ID="chkselect" runat="server" />
            </ItemTemplate>
        </asp:TemplateField>
        <asp:BoundField DataField="CustomerId" HeaderText="Id" />
        <asp:BoundField DataField="Name" HeaderText="Name" />
        <asp:TemplateField HeaderText="Country">
            <ItemTemplate>
                <asp:DropDownList runat="server" ID="ddlCountry"></asp:DropDownList>
            </ItemTemplate>
        </asp:TemplateField>
        <asp:TemplateField>
            <ItemTemplate>
                <asp:ImageButton ID="imgbtn" runat="server" OnClick="OnUpdate" />
            </ItemTemplate>
        </asp:TemplateField>
    </Columns>
</asp:GridView><br /><br />
<asp:Label ID="lblName" runat="server">Name</asp:Label>
<asp:TextBox ID="txtName" runat="server"></asp:TextBox>

Namespaces

C#

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

VB.Net

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

Code

C#

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

protected void OnUpdate(object sender, EventArgs e)
{
    ImageButton imgbtn = (ImageButton)sender;
    GridViewRow GridView1Row = (GridViewRow)imgbtn.NamingContainer;
    DropDownList ddl = (DropDownList)(GridView1Row.Cells[3].Controls[0].FindControl("ddlCountry"));
    string t_ddl = ddl.Text;
    foreach (GridViewRow row in GridView1.Rows)
    {
        CheckBox chkSelect = (CheckBox)row.FindControl("chkSelect");
        if (chkSelect.Checked && !String.IsNullOrEmpty(t_ddl.ToString()))
        {
            int id = int.Parse(row.Cells[1].Text);
            string constring = ConfigurationManager.ConnectionStrings["constr"].ConnectionString;
            using (SqlConnection con = new SqlConnection(constring))
            {
                using (SqlCommand cmd = new SqlCommand("UPDATE Customers SET Name=@Name WHERE CustomerId=@CustomerId", con))
                {
                    con.Open();
                    cmd.Parameters.AddWithValue("@Name", txtName.Text);
                    cmd.Parameters.AddWithValue("@CustomerId", id);
                    cmd.ExecuteNonQuery();
                    con.Close();
                }
            }
        }
    }
    this.GridView();
}

protected void OnRowDataBound(object sender, GridViewRowEventArgs e)
{
    if (e.Row.RowType == DataControlRowType.DataRow)
    {
        string conString = ConfigurationManager.ConnectionStrings["constr"].ConnectionString;
        using (SqlConnection con = new SqlConnection(conString))
        {
            using (SqlCommand cmd = new SqlCommand("SELECT CustomerId, Name, Country FROM Customers", con))
            {
                con.Open();
                DropDownList ddlCountry = (e.Row.FindControl("ddlCountry") as DropDownList);
                ddlCountry.DataTextField = "Country";
                ddlCountry.DataValueField = "CustomerId";
                ddlCountry.DataSource = cmd.ExecuteReader();
                ddlCountry.DataBind();
                con.Close();
            }
        }
    }
}

private void GridView()
{
    string constring = ConfigurationManager.ConnectionStrings["constr"].ConnectionString;
    using (SqlConnection con = new SqlConnection(constring))
    {
        using (SqlCommand cmd = new SqlCommand("SELECT * FROM Customers", con))
        {
            using (SqlDataAdapter sda = new SqlDataAdapter(cmd))
            {
                using (DataTable dt = new DataTable())
                {
                    sda.Fill(dt);
                    GridView1.DataSource = dt;
                    GridView1.DataBind();
                }
            }
        }
    }
}

VB.Net

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

Protected Sub OnUpdate(ByVal sender As Object, ByVal e As EventArgs)
    Dim imgbtn As ImageButton = CType(sender, ImageButton)
    Dim GridView1Row As GridViewRow = CType(imgbtn.NamingContainer, GridViewRow)
    Dim ddl As DropDownList = CType((GridView1Row.Cells(3).Controls(0).FindControl("ddlCountry")), DropDownList)
    Dim t_ddl As String = ddl.Text
    For Each row As GridViewRow In GridView1.Rows
        Dim chkSelect As CheckBox = CType(row.FindControl("chkSelect"), CheckBox)
        If chkSelect.Checked AndAlso Not String.IsNullOrEmpty(t_ddl.ToString()) Then
            Dim id As Integer = Integer.Parse(row.Cells(1).Text)
            Dim constring As String = ConfigurationManager.ConnectionStrings("constr").ConnectionString
            Using con As SqlConnection = New SqlConnection(constring)
                Using cmd As SqlCommand = New SqlCommand("UPDATE Customers SET Name=@Name WHERE CustomerId=@CustomerId", con)
                    con.Open()
                    cmd.Parameters.AddWithValue("@Name", txtName.Text)
                    cmd.Parameters.AddWithValue("@CustomerId", id)
                    cmd.ExecuteNonQuery()
                    con.Close()
                End Using
            End Using
        End If
    Next
    Me.GridView()
End Sub

Protected Sub OnRowDataBound(ByVal sender As Object, ByVal e As GridViewRowEventArgs)
    If e.Row.RowType = DataControlRowType.DataRow Then
        Dim conString As String = ConfigurationManager.ConnectionStrings("constr").ConnectionString
        Using con As SqlConnection = New SqlConnection(conString)
            Using cmd As SqlCommand = New SqlCommand("SELECT CustomerId, Name, Country FROM Customers", con)
                con.Open()
                Dim ddlCountry As DropDownList = (TryCast(e.Row.FindControl("ddlCountry"), DropDownList))
                ddlCountry.DataTextField = "Country"
                ddlCountry.DataValueField = "CustomerId"
                ddlCountry.DataSource = cmd.ExecuteReader()
                ddlCountry.DataBind()
                con.Close()
            End Using
        End Using
    End If
End Sub

Private Sub GridView()
    Dim constring As String = ConfigurationManager.ConnectionStrings("constr").ConnectionString
    Using con As SqlConnection = New SqlConnection(constring)
        Using cmd As SqlCommand = New SqlCommand("SELECT * FROM Customers", con)
            Using sda As SqlDataAdapter = New SqlDataAdapter(cmd)
                Using dt As DataTable = New DataTable()
                    sda.Fill(dt)
                    GridView1.DataSource = dt
                    GridView1.DataBind()
                End Using
            End Using
        End Using
    End Using
End Sub

Screenshot