Re-populating checkboxlist in Edit Mode from SQL comma-separated string is not selecting checkboxes

Question

I am not able to pre-populate CheckBoxList3 in my app. I have successfully retrieved string data from database and passed to array but routine fails with:

NullReferenceException:Object not set to instance of an object error at line:
ListItem currentCheckBox = cb3.Items.FindByValue(items[i].ToString());

readMyString() method uses SqlDataReader to read and split a string column from SQL table then pass the values for example: "A, B, C" to string array to identify which of 6 checkboxes should be selected. Code reference: [http://mikesdotnetting.com/Article/53/Saving-a-user's-CheckBoxList-selection-and-re-populating-the-CheckBoxList-from-saved-data]

HTML CODE:

<asp:GridView ID="GridView1" runat="server" 
              AutoGenerateColumns="False" CellPadding="4" DataKeyNames="MyID"   
              DataSourceID="sdsmyTable1" ForeColor="#333333" GridLines="None" 
              onrowdeleted="GridView1_RowDeleted" 
              onrowdeleting="GridView1_RowDeleting" 
              onrowupdated="GridView1_RowUpdated"  
              onrowupdating="GridView1_RowUpdating" 
              onselectedindexchanged="GridView1_SelectedIndexChanged" 
              onrowediting="GridView1_RowEditing" 
              onrowcancelingedit="GridView1_RowCancelingEdit" 
              onrowdatabound="GridView1_RowDataBound">
    <RowStyle BackColor="#EFF3FB" />

    <Columns>
        <asp:CommandField ShowDeleteButton="True" ShowEditButton="True" />

        <asp:BoundField DataField="myID" HeaderText="myID" ReadOnly="True" 
                        SortExpression="myID" />

        <asp:BoundField DataField="Date1" HeaderText="Date driver lic issued" 
                        SortExpression="Date1" />

        <asp:TemplateField HeaderText="chooseOne" SortExpression="chooseOne">
            <ItemTemplate>
                <asp:Label ID="Label1" runat="server" Text='<%# Bind("chooseOne") %>'></asp:Label>
            </ItemTemplate>
            <EditItemTemplate>                
                <asp:RadioButtonList ID="RadioButtonList2" runat="server" SelectedValue='<%# Bind("chooseOne") %>' Font-Size="Small" 
                                     RepeatDirection="Horizontal">
                    <asp:ListItem Value="1">1</asp:ListItem>
                    <asp:ListItem Value="2">2</asp:ListItem>
                    <asp:ListItem Value="3">3</asp:ListItem>
                </asp:RadioButtonList>
            </EditItemTemplate>

        </asp:TemplateField>
        <asp:TemplateField HeaderText="MyCommaSeparatedString" SortExpression="MyCommaSeparatedString">
            <ItemTemplate>
                <asp:Label ID="Label2" runat="server" Text='<%# Bind("MyCommaSeparatedString") %>'></asp:Label>
            </ItemTemplate>
            <EditItemTemplate>
                <asp:TextBox ID="TextBox2" runat="server" Text='<%# Bind("MyCommaSeparatedString") %>'></asp:TextBox>
                <asp:CheckBoxList ID="CheckBoxList3" runat="server" Font-Size="Small"  
                                  RepeatDirection="Horizontal">                              
                    <asp:ListItem Value="A">A</asp:ListItem>
                    <asp:ListItem Value="B">B</asp:ListItem>
                    <asp:ListItem Value="C">C</asp:ListItem>                   
                    <asp:ListItem Value="D">D</asp:ListItem>
                    <asp:ListItem Value="E">E</asp:ListItem>
                    <asp:ListItem Value="F">F</asp:ListItem>           
                </asp:CheckBoxList>
            </EditItemTemplate>

C# Code:

    protected void GridView1_RowDataBound(object sender, GridViewRowEventArgs e)
        {
            //// establish a datarow to dig into its minutia
            DataRowView drv = e.Row.DataItem as DataRowView;

            // if 1: RowType of gridview control is a datarow 
            if (e.Row.RowType == DataControlRowType.DataRow)
            {
                //if 2: is datarow in edit mode
                if ((e.Row.RowState & DataControlRowState.Edit) > 0)
                {
                  RadioButtonList rb2 = (RadioButtonList)e.Row.FindControl("RadioButtonList2");
                  CheckBoxList cb3 = (CheckBoxList)e.Row.FindControl("CheckBoxList3");
//CheckBoxList cb3 = (CheckBoxList)GridView1.Rows[GridView1.EditIndex].FindControl("CheckBoxList3");
                  CheckBoxList cb4 = (CheckBoxList)e.Row.FindControl("CheckBoxList4");

                    // Create an instance of SqlConn class            
                    SqlConnClass getMyStr= new SqlConnClass();

                    //Return datareader to read Endorsements column from database
                    SqlDataReader rdr = getMyStr.selectMyString(GetMyID());

                    try
                    {
                        // column
                        if (rb2 != null)
                        {
                            rb2.SelectedValue = drv[2].ToString();
                        }

                        // column                    
                        //CheckBoxList cb3 = (CheckBoxList)e.Row.FindControl("CheckBoxList3");
                        if (cb3 != null)//if (cb3 contains 6 checkboxes (I, N, H, X, T, K)
                        {
                            //bind checkbox manually
                            cb3.DataSource = sdsDatasource;
                            cb3.DataTextField = "MyCommaSeparatedString ";
                            cb3.DataValueField = "MyCommaSeparatedString ";
                            cb3.DataBind();

                            // if row exists
                            if (rdr.HasRows)//(dt.Rows.Count > 0 && dt != null)
                            {
                                //start reading
                                rdr.Read();

                //extract comma separated string from datareader into one-dimensional array    
                                string[] items = rdr.GetString(0).Split(',');

               //returns the upper bound for the indexes of the first dimension of the Array
                                for (int i = 0; i <= items.GetUpperBound(0); i++)
                                {
              // currentCheckBox IS WHERE NULL OCCURS: 
              ListItem currentCheckBox = cb3.Items.FindByValue(items[i].ToString());

                                    if (currentCheckBox != null)
                                    {
                                        currentCheckBox.Selected = true;
                                    }
                                    //cb3.SelectedValue = drv[3].ToString();
                                    //}
                                }// end of for

                                //close SqlDataReader
                                rdr.Close();
                            }

                        // column
                        //CheckBoxList cb4 = (CheckBoxList)e.Row.FindControl("CheckBoxList4");
                        if (cb4 != null)
                        {
                            cb4.SelectedValue = drv[4].ToString();
                        }

                        }// end of if
                    }// end of try

                    catch (IndexOutOfRangeException ex2)
                    {
    System.Diagnostics.Debug.WriteLine(ex2.Message + "; " + ex2.Source + "; " + ex2.TargetSite);
                    }//end of catch                
                }// end of if (rowstate)
            } // end of if (rowtype)
        }// end of method

What I have tried: calling readMyString() method from GridView1_RowDataBound event and/or from GridView1_RowEditing event.

Since CheckBoxList3 is empty to begin with and seems to not want to be null, I added the line cb3.Items[i].Value = items[i]; but the error just moves to the new line instead. I must be missing something.

Can anyone see where I've errored? I must be putting the code in the wrong methods...?

Answer 1

You are trying to find the control in the GridView. The controls are inside the GridView Rows. So you need to do something like this:

CheckBoxList cb3 = (CheckBoxList) GridView1.Rows[GridView1.EditIndex].FindControl("CheckBoxList3");

Trim the items[i] like below:

ListItem currentCheckBox = cb3.Items.FindByValue(items[i].Trim());