[Solved] ASP.Net GridView Control Find Error: Object reference not set to an instance of an object

makumbi says:

cmd.Parameters.AddWithValue("@CustomerId", row.Cells(11).Controls.OfType(Of TextBox)().FirstOrDefault().Text)

Change with below. TextBox should be LinkButton.

cmd.Parameters.AddWithValue("@CustomerId", row.Cells(11).Controls.OfType(Of LinkButton)().FirstOrDefault().Text)

Please refer below sample.

Note: For this sample i have used temporary DataTable. For more details refer How to create Temporary Table in ASP.Net using C# and VB.Net.

HTML

<asp:UpdatePanel ID="UpdatePanel2" runat="server">
<ContentTemplate>
<asp:GridView ID="Gvgridclient" runat="server" AutoGenerateColumns="False" ShowFooter="True">
    <Columns>
        <asp:TemplateField HeaderText="ItemCode">
            <ItemTemplate>
                <asp:TextBox ID="txtItemCode" runat="server" Text='<%# Bind("ItemCode") %>'></asp:TextBox>
            </ItemTemplate>
        </asp:TemplateField>
        <asp:BoundField DataField="ItemDescription" HeaderText="ItemDescription" />
        <asp:BoundField DataField="ItemSize" HeaderText="ItemSize" />
        <asp:TemplateField HeaderText="Quantity">
            <EditItemTemplate>
                <asp:TextBox ID="Quantity" runat="server" Text='<%# Bind("Quantity") %>'></asp:TextBox>
            </EditItemTemplate>
            <FooterTemplate>
                <asp:TextBox ID="Fqty" runat="server" Width="46px"></asp:TextBox>
            </FooterTemplate>
            <ItemTemplate>
                <asp:TextBox ID="txtQuantity" runat="server" AutoPostBack="true" Text='<%# Eval("Quantity") %>' Width="46px"></asp:TextBox>
            </ItemTemplate>
        </asp:TemplateField>
        <asp:BoundField DataField="OrderPrice" HeaderText="OrderPrice" />
        <asp:TemplateField HeaderText="SalePrice">
            <EditItemTemplate>
                <asp:TextBox ID="TextBox3" runat="server" Text='<%# Bind("SalePrice") %>'></asp:TextBox>
            </EditItemTemplate>
            <ItemTemplate>
                <asp:Label ID="Label1" runat="server" Text='<%# Bind("SalePrice") %>' Visible="False"></asp:Label>
                <asp:TextBox ID="txtSalePrice" runat="server" Text='<%# Eval("SalePrice") %>' Width="85px" Height="16px"></asp:TextBox>
            </ItemTemplate>
        </asp:TemplateField>
        <asp:TemplateField HeaderText="SubTotal">
            <EditItemTemplate>
                <asp:TextBox ID="TextBox2" runat="server"></asp:TextBox>
            </EditItemTemplate>
            <FooterTemplate>
                <asp:TextBox ID="txtFsubtotal" runat="server" Width="46px"></asp:TextBox>
            </FooterTemplate>
            <ItemTemplate>
                <asp:Label ID="lblsubtotal" runat="server" Text='<%# Bind("SubTotal") %>'></asp:Label>
                <asp:TextBox ID="txtsubtotal" runat="server" Height="16px" Text='<%# Eval("SubTotal") %>' Width="75px"></asp:TextBox>
            </ItemTemplate>
        </asp:TemplateField>
        <asp:BoundField DataField="Prno" HeaderText="Prno" />
        <asp:BoundField DataField="Names" HeaderText="Names" />
        <asp:BoundField DataField="Date" HeaderText="Date" />
        <asp:TemplateField HeaderText="DelSingle">
            <ItemTemplate>
                <asp:LinkButton ID="lnkRemove" runat="server" Text="Delete"></asp:LinkButton>
            </ItemTemplate>
        </asp:TemplateField>
        <asp:TemplateField HeaderText="Key">
            <ItemTemplate>
                <asp:LinkButton ID="lnkUpdate" runat="server" Text="Update" OnClick="Update"></asp:LinkButton>
                <%-- <asp:TextBox ID="Classcode" runat="server" Height="16px" Visible="True" Text='<%# Bind("Keyfield") %>' Width="54px"></asp:TextBox>--%>
            </ItemTemplate>
        </asp:TemplateField>
    </Columns>
</asp:GridView>
</ContentTemplate>
</asp:UpdatePanel>

Namespaces

C#

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

VB.Net

Imports System.Data
Imports System.Data.SqlClient

Code

C#

protected void Page_Load(object sender, EventArgs e)
{
    if (!this.IsPostBack)
    {
        DataTable dt = new DataTable();
        dt.Columns.AddRange(new DataColumn[12] {
            new DataColumn("ItemCode"),
            new DataColumn("ItemDescription"),
            new DataColumn("ItemSize"),
            new DataColumn("Quantity"),
            new DataColumn("OrderPrice"),
            new DataColumn("SalePrice"),
            new DataColumn("SubTotal"),
            new DataColumn("Prno"),
            new DataColumn("Names"),
            new DataColumn("Date"),
            new DataColumn("DelSingle"),
            new DataColumn("Key")});
        dt.Rows.Add("012", "Item 1", "5cm", "40", "10", "450", "4510", "04215", "Excel", "10/04/2022", "");
        dt.Rows.Add("013", "Item 2", "6cm", "70", "80", "820", "5361", "0258", "Word", "04/05/2022", "");
        dt.Rows.Add("014", "Item 3", "4cm", "210", "59", "890", "8468", "85642", "Text", "18/06/2022", "");
        dt.Rows.Add("015", "Item 4", "9cm", "440", "70", "40", "8120", "47258", "Items", "20/07/2022", "");
        dt.Rows.Add("016", "Item 5", "7cm", "450", "80", "50", "9812", "69140", "Excel", "31/08/2022", "");
        Gvgridclient.DataSource = dt;
        Gvgridclient.DataBind();
    }
}

protected void Update(object sender, EventArgs e)
{
    foreach (GridViewRow row in Gvgridclient.Rows)
    {
        if (row.RowType == DataControlRowType.DataRow)
        {
            bool isChecked = row.Cells[0].Controls.OfType<CheckBox>().FirstOrDefault().Checked;
            if (isChecked)
            {
                SqlCommand cmd = new SqlCommand("UPDATE [order] SET qty = @qty, Subtotal = @subtotal, saleprice=@saleprice, itemcode=@svalue WHERE keycode = @CustomerId");
                cmd.Parameters.AddWithValue("@qty", row.Cells[4].Controls.OfType<TextBox>().FirstOrDefault().Text);
                cmd.Parameters.AddWithValue("@subtotal", row.Cells[6].Controls.OfType<TextBox>().FirstOrDefault().Text);
                cmd.Parameters.AddWithValue("@saleprice", row.Cells[5].Controls.OfType<TextBox>().FirstOrDefault().Text);
                cmd.Parameters.AddWithValue("@svalue", row.Cells[1].Controls.OfType<TextBox>().FirstOrDefault().Text);
                string kk = row.Cells[11].Controls.OfType<LinkButton>().FirstOrDefault().Text;
                cmd.Parameters.AddWithValue("@CustomerId", row.Cells[11].Controls.OfType<LinkButton>().FirstOrDefault().Text);
                cmd.ExecuteNonQuery(); 
            }
        }
    }
}

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(11) {New DataColumn("ItemCode"), New DataColumn("ItemDescription"), New DataColumn("ItemSize"), New DataColumn("Quantity"), New DataColumn("OrderPrice"), New DataColumn("SalePrice"), New DataColumn("SubTotal"), New DataColumn("Prno"), New DataColumn("Names"), New DataColumn("Date"), New DataColumn("DelSingle"), New DataColumn("Key")})
        dt.Rows.Add("012", "Item 1", "5cm", "40", "10", "450", "4510", "04215", "Excel", "10/04/2022", "")
        dt.Rows.Add("013", "Item 2", "6cm", "70", "80", "820", "5361", "0258", "Word", "04/05/2022", "")
        dt.Rows.Add("014", "Item 3", "4cm", "210", "59", "890", "8468", "85642", "Text", "18/06/2022", "")
        dt.Rows.Add("015", "Item 4", "9cm", "440", "70", "40", "8120", "47258", "Items", "20/07/2022", "")
        dt.Rows.Add("016", "Item 5", "7cm", "450", "80", "50", "9812", "69140", "Excel", "31/08/2022", "")
        Gvgridclient.DataSource = dt
        Gvgridclient.DataBind()
    End If
End Sub

Protected Sub Update(ByVal sender As Object, ByVal e As EventArgs)
    For Each row As GridViewRow In Gvgridclient.Rows

        If row.RowType = DataControlRowType.DataRow Then
            Dim isChecked As Boolean = row.Cells(0).Controls.OfType(Of CheckBox)().FirstOrDefault().Checked

            If isChecked Then
                Dim cmd As SqlCommand = New SqlCommand("UPDATE [order] SET qty = @qty, Subtotal = @subtotal, saleprice=@saleprice, itemcode=@svalue WHERE keycode = @CustomerId")
                cmd.Parameters.AddWithValue("@qty", row.Cells(4).Controls.OfType(Of TextBox)().FirstOrDefault().Text)
                cmd.Parameters.AddWithValue("@subtotal", row.Cells(6).Controls.OfType(Of TextBox)().FirstOrDefault().Text)
                cmd.Parameters.AddWithValue("@saleprice", row.Cells(5).Controls.OfType(Of TextBox)().FirstOrDefault().Text)
                cmd.Parameters.AddWithValue("@svalue", row.Cells(1).Controls.OfType(Of TextBox)().FirstOrDefault().Text)
                Dim kk As String = row.Cells(11).Controls.OfType(Of LinkButton)().FirstOrDefault().Text
                cmd.Parameters.AddWithValue("@CustomerId", row.Cells(11).Controls.OfType(Of LinkButton)().FirstOrDefault().Text)
                cmd.ExecuteNonQuery()
            End If
        End If
    Next
End Sub

Screenshot