Question

我无法在我的应用中预先填充CheckBoxList3。我已成功从数据库中检索字符串数据并传递给数组，但例程失败：

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

readMyString（）方法使用SqlDataReader从SQL表中读取和拆分字符串列，然后将值例如：“A，B，C”传递给字符串数组，以标识应选择6个复选框中的哪一个。代码参考：[http://mikesdotnetting.com/Article/53/Saving-a-user's-CheckBoxList-selection-and-rempolulation-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＃代码：

    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

我尝试过：从GridView1_ RowDataBound 事件和/或从GridView1_ RowEditing 事件调用readMyString（）方法。

由于CheckBoxList3开头为空并且似乎不想为null，我添加了行cb3.Items[i].Value = items[i];，但错误只是移动到新行。我一定错过了什么。

谁能看到我的错误？我必须把代码放在错误的方法中......？

Answer 1

您正在尝试在GridView中找到该控件。控件位于GridView Rows中。所以你需要做这样的事情：

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

修剪下面的项目[i]：

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

在编辑模式下从SQL逗号分隔字符串重新填充复选框列表不是选中复选框

1 个答案: