Question

I want to update data when I checked in gridview. Before I shoude get value from checkbox but my code return data from database only. I want current value after I checked.

CodeBehind:-

protected void chkSelected_CheckedChanged(object sender, EventArgs e)
{
    for (int rowIndex = 0; rowIndex < GridView1.Rows.Count; rowIndex++)
    {
        if (Convert.ToString(GridView1.Rows[rowIndex].Cells[4].Text) != "")
        {
            Response.Write("true");
        }
        else
        {
            Response.Write("fasle");
        }
    }
}

Design Code:-

<asp:GridView ID="GridView1" runat="server" DataSourceID="SqlDataSource1"
              CellPadding="4" GridLines="None" ForeColor="#333333" Font-Size="Smaller" 
              AutoGenerateColumns="False">
    <RowStyle BackColor="#EFF3FB" />
    <Columns>
        <asp:BoundField DataField="LevelID" HeaderText="ลำดับข้อ" ReadOnly="True" 
                        ItemStyle-Width="50"  >
        </asp:BoundField>
        <asp:BoundField DataField="LevelDesc" HeaderText="คำถาม" ReadOnly="True" 
                        ItemStyle-Width="250"  >
        </asp:BoundField>
        <asp:BoundField DataField="ChoiceID" HeaderText="ข้อย่อย" ReadOnly="True" 
                        ItemStyle-Width="50"  >
        </asp:BoundField>
        <asp:BoundField DataField="ChoiceDesc" HeaderText="คำถามย่อย" ReadOnly="True" 
                        ItemStyle-Width="400"  >
        </asp:BoundField>
        <asp:TemplateField HeaderText="ใช่">          
            <ItemTemplate>              
                <asp:CheckBox ID="chkSelected" runat="server" Checked='<%# Eval("Selected").ToString().Equals("True") %>'
                     AutoPostBack="true" OnCheckedChanged="chkSelected_CheckedChanged" CssClass="chkBox" />          
            </ItemTemplate>       
        </asp:TemplateField> 
    </Columns>
    <FooterStyle BackColor="#507CD1" ForeColor="White" Font-Bold="True" />
    <PagerStyle BackColor="#2461BF" ForeColor="White" HorizontalAlign="Center" />
    <SelectedRowStyle BackColor="#D1DDF1" Font-Bold="True" ForeColor="#333333" />
    <HeaderStyle BackColor="#0000CD" Font-Bold="True" ForeColor="White" />
    <EditRowStyle BackColor="#2461BF" />
    <AlternatingRowStyle BackColor="White" />
</asp:GridView>

Answer 1

use GridViewRow as follow…You can get the current row of the checkbox which is checked using NamingContainer property as follow…

Edit:-
Change the markup and add Hiddenfield to hold value for Selected as follow…

<asp:TemplateField HeaderText="ใช่">          
            <ItemTemplate>              
                <asp:CheckBox ID="chkSelected" runat="server"  Checked='<%# Eval("Selected").ToString().Equals("True") %>'
                     AutoPostBack="true" OnCheckedChanged="chkSelected_CheckedChanged" CssClass="chkBox" />     
                <asp:HiddenField ID="hiddenField1" Value='<%# Eval("Selected").ToString() %>' runat="server" />    
            </ItemTemplate>       
 </asp:TemplateField> 

Then you can get the Hiddenfield as follow and it’s value as well

protected void chkSelected_CheckedChanged(object sender, EventArgs e)
    {
         GridViewRow row = (GridViewRow)(((CheckBox)sender).NamingContainer);
         HiddenField hdnCheck=(HiddenField)row.Cells[4].FindControl("hiddenField1");
         if (Convert.ToString(hdnCheck.Value != "")
           {
               Response.Write("true");
           }
           else
           {
               Response.Write("false");
           }

         // Edit: You can easily get Checkbox which has been checked, and do your logic
         CheckBox chkSelect=(CheckBox)sender;
         if (chkSelect.Checked)
           {
               Response.Write("true");
           }
           else
           {
               Response.Write("false");
           }    
    }