保存到数据库时，选择“所有复选框”按钮错误

时间：2013-10-09 00:31:51

标签： c# asp.net sql-server nullreferenceexception detailsview

这是this thread with how to build a DetailsView button that will check all the boxes in a given form.的延续我尝试在前一个帖子中获得帮助，但没有响应，因此新线程。

截至目前，复选框按钮无问题，但当我点击“保存”按钮时，此行的cs文件中会显示一条错误消息：

                TextBox tb = FindControl<TextBox>(row.Cells[i].Controls);
                if (tb != null)
                {
                    table.Rows[0][j] = tb.Text;
                }

错误：

System.NullReferenceException：未将对象引用设置为对象的实例。

我很难过，我在这里做错了什么。我想我不知道这个过程如何在幕后完全运作。我一直在倾注MSDN文档，看看我是否可以更好地解释如何在理论上正确地将其保存到数据库，但是无法找到合适的文档来帮助。

在我向代码添加复选框按钮之前，SQL代码是可靠的并且没有任何问题。

表格代码：

(Note some cosmetic code for the details view has been omitted)


<%@ Page Title="Test Page" Language="C#" MasterPageFile="~/Site.master" AutoEventWireup="true" CodeFile="form2.aspx.cs" Inherits="form2" %>   
<asp:Content ID="Content1" ContentPlaceHolderID="HeadContent" Runat="Server">
</asp:Content>
<asp:Content ID="Content2" ContentPlaceHolderID="FeaturedContent" Runat="Server">
</asp:Content>
<asp:Content ID="Content3" ContentPlaceHolderID="MainContent" Runat="Server">
<asp:DetailsView ID="DetailsView" runat="server" AutoGenerateColumns="False" CellPadding="4" DataSourceID="SqlDataSource1" ForeColor="#333333" GridLines="None">
<AlternatingRowStyle BackColor="White" />
<insert asp cosmetic gobbledy gook here>
<Fields>
    <asp:BoundField DataField="Field_1" HeaderText="Ticket Number" SortExpression="Field_1" />
    <asp:BoundField DataField="Field 2" HeaderText="Field 2" SortExpression="Field_2" />
    <asp:BoundField DataField="Field_3" HeaderText="Field 3" SortExpression="Field_3" />
    <asp:BoundField DataField="Field_4" HeaderText="Field 4" SortExpression="Field_4" />
    <asp:BoundField DataField="Field_5" HeaderText="Field 5" SortExpression="Field_5" />
    <asp:BoundField DataField="Field_6" HeaderText="Field 6" SortExpression="Field_6" />
    <asp:BoundField DataField="Field_7" HeaderText="Field 7" SortExpression="Field_7" />
    <asp:BoundField DataField="Field_8" HeaderText="Field 8" SortExpression="Field_8" />
    <asp:BoundField DataField="Field_9" HeaderText="Field 9" SortExpression="Field_9" />
    <asp:BoundField DataField="Field_10" HeaderText="Field 10" SortExpression="Field_10" />
    <asp:CheckBoxField DataField="Check_Box_1" HeaderText="Check Box 1" SortExpression="Check_Box_1" />
    <asp:CheckBoxField DataField="Check_Box_2" HeaderText="Check Box 2" SortExpression="Check_Box_2" />
    <asp:CheckBoxField DataField="Check_Box_3" HeaderText="Check Box 3" SortExpression="Check_Box_3" />
    <asp:CheckBoxField DataField="Check_Box_4" HeaderText="Check Box 4" SortExpression="Check_Box_4" />
    <asp:CheckBoxField DataField="Check_Box_5" HeaderText="Check Box 5" SortExpression="Check_Box_5" />
    <asp:CheckBoxField DataField="Check_Box_6" HeaderText="Check Box 6" SortExpression="Check_Box_6" />
    <asp:CheckBoxField DataField="Check_Box_7" HeaderText="Check Box 7" SortExpression="Check_Box_7" />
    <asp:CheckBoxField DataField="Check_Box_8" HeaderText="Check Box 8" SortExpression="Check_Box_8" />
    <asp:CheckBoxField DataField="Check_Box_9" HeaderText="Check Box 9" SortExpression="Check_Box_9" />
    <asp:CheckBoxField DataField="Check_Box_10" HeaderText="Check Box 10" SortExpression="Check_Box_10" />
    <asp:CheckBoxField DataField="Check_Box_11" HeaderText="Check Box 11" SortExpression="Check_Box_11" />
    <asp:CheckBoxField DataField="Check_Box_12" HeaderText="Check Box 12" SortExpression="Check_Box_12" />
    <asp:CheckBoxField DataField="Check_Box_13" HeaderText="Check Box 13" SortExpression="Check_Box_13" />
    <asp:CheckBoxField DataField="Check_Box_14" HeaderText="Check Box 14" SortExpression="Check_Box_14" />
    <asp:CheckBoxField DataField="Check_Box_15" HeaderText="Check Box 15" SortExpression="Check_Box_15" />
    <asp:CheckBoxField DataField="Check_Box_16" HeaderText="Check Box 16" SortExpression="Check_Box_16" />
    <asp:CheckBoxField DataField="Check_Box_17" HeaderText="Check Box 17" SortExpression="Check_Box_17" />
    <asp:CheckBoxField DataField="Check_Box_18" HeaderText="Check Box 18" SortExpression="Check_Box_18" />
    <asp:CheckBoxField DataField="Check_Box_19" HeaderText="Check Box 19" SortExpression="Check_Box_19" />


    <asp:ButtonField ButtonType="Button" CommandName="btnSelectAll" Text="Select/Check All Servers" >


    <asp:BoundField DataField="Field_11" HeaderText="Field 11" SortExpression="Field_11" />
    <asp:BoundField DataField="Field_12" HeaderText="Field 12" SortExpression="Field_12" />
    <asp:BoundField DataField="Field_13" HeaderText="Field 13" SortExpression="Field_13" />


    <asp:ButtonField ButtonType="Button" CommandName="btnCancel" Text="Cancel" />
    <asp:ButtonField ButtonType="Button" CommandName="btnSave" Text="Save" />

    <asp:CommandField ButtonType="Button" NewText="CreateRecord" ShowInsertButton="True" />
</Fields>
<more asp non essential cosmetic gobbledy gook>

    </asp:DetailsView>
    <asp:SqlDataSource ID="SqlDataSource1" ConnectionString="<%$ ConnectionStrings:test_form_connect %>" runat="server" InsertCommand="INSERT INTO [test].[detailsview_test_form] ([Field_1], [Field_2], [Field_3], [Field_4], [Field_5], [Field_6], [Field_7], [Field_8], [Field_9], [Field_10], [Check_Box_1], [Check_Box_2], [Check_Box_3], [Check_Box_4], [Check_Box_5], [Check_Box_6], [Check_Box_7], [Check_Box_8], [Check_Box_9], [Check_Box_10], [Check_Box_11], [Check_Box_12], [Check_Box_13], [Check_Box_14], [Check_Box_15], [Check_Box_16], [Check_Box_17], [Check_Box_18], [Check_Box_19], [Field_11], [Field_12], [Field_13]) VALUES (@Field_1, @Field_2, @Field_3, @Field_4, @Field_5, @Field_6, @Field_7, @Field_8, @Field_9, @Field_10, @Check_Box_1, @Check_Box_2, @Check_Box_3, @Check_Box_4, @Check_Box_5, @Check_Box_6, @Check_Box_7, @Check_Box_8, @Check_Box_9, @Check_Box_10, @Check_Box_11, @Check_Box_12, @Check_Box_13, @Check_Box_14, @Check_Box_15, @Check_Box_16, @Check_Box_17, @Check_Box_18, @Check_Box_19, @Field_11, @Field_12, @Field_13) ">

    <InsertParameters>
<asp:Parameter Name="Field_1" />
<asp:Parameter Name="Field_2" />
<asp:Parameter Name="Field_3" />
<asp:Parameter Name="Field_4" />
<asp:Parameter Name="Field_5" />
<asp:Parameter Name="Field_6" />
<asp:Parameter Name="Field_7" />
<asp:Parameter Name="Field_8" />
<asp:Parameter Name="Field_9" />
<asp:Parameter Name="Field_10" />
<asp:Parameter Name="Check_Box_1" />
<asp:Parameter Name="Check_Box_2" />
<asp:Parameter Name="Check_Box_3" />
<asp:Parameter Name="Check_Box_4" />
<asp:Parameter Name="Check_Box_5" />
<asp:Parameter Name="Check_Box_6" />
<asp:Parameter Name="Check_Box_7" />
<asp:Parameter Name="Check_Box_8" />
<asp:Parameter Name="Check_Box_9" />
<asp:Parameter Name="Check_Box_10" />
<asp:Parameter Name="Check_Box_11" />
<asp:Parameter Name="Check_Box_12" />
<asp:Parameter Name="Check_Box_13" />
<asp:Parameter Name="Check_Box_14" />
<asp:Parameter Name="Check_Box_15" />
<asp:Parameter Name="Check_Box_16" />
<asp:Parameter Name="Check_Box_17" />
<asp:Parameter Name="Check_Box_18" />
<asp:Parameter Name="Check_Box_19" />
<asp:Parameter Name="Field_11" />
<asp:Parameter Name="Field_12" />
<asp:Parameter Name="Field_13" />

        </InsertParameters>
        </asp:SqlDataSource>


</asp:Content>

背后的代码

using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Data;
using System.Data.SqlClient;

public partial class checkbox_dev : System.Web.UI.Page
{
DataTable m_table = null;

public DataTable table

{
    get
    {
        if (ViewState["m_table"] != null)
            return (DataTable)ViewState["m_table"];
        else
            return null;
    }
    set
    {
        ViewState["m_table"] = value;
    }
}

public static T FindControl<T>(ControlCollection controls)
{
    for (int i = 0; i < controls.Count; i++)
    {
        if (controls[i] is T)
            return (T)(object)controls[i];
    }

    return default(T);
}

protected void Page_Load(object sender, EventArgs e)
//private static DataTable GetData(string sqlCommand)
{
    string connectionString = GetConnectionString();
    SqlConnection connection = new SqlConnection(connectionString);
}

static private string GetConnectionString()
{
    return "(insert SQL Server connection Stringhere)";
}



protected void DetailsView1_ItemCommand(Object sender, DetailsViewCommandEventArgs e)
{
    if (e.CommandName == "btnSelectAll")
    {
        foreach (DetailsViewRow row in DetailsView1.Rows)
        {
            for (int i = 0; i < row.Cells.Count; i++)
            {
                CheckBox cb = FindControl<CheckBox>(row.Cells[i].Controls);
                if (cb != null)
                {
                    cb.Checked = true;
                }
            }
        }
    }
    if (e.CommandName == "btnSave")
    {
        int j = 0;
        foreach (DetailsViewRow row in DetailsView1.Rows)
        {
            for (int i = 0; i < row.Cells.Count; i++)
            {
                TextBox tb = FindControl<TextBox>(row.Cells[i].Controls);
                if (tb != null)
                {
                    table.Rows[0][j] = tb.Text;
                }

                CheckBox cb = FindControl<CheckBox>(row.Cells[i].Controls);
                if (cb != null)
                {
                    table.Rows[0][j] = cb.Checked;
                }
            }
            j++;
        }

        DetailsView1.ChangeMode(DetailsViewMode.ReadOnly);
        DetailsView1.DataSource = table;
        DetailsView1.DataBind();
    }
    if (e.CommandName == "btnEdit")
    {
        DetailsView1.ChangeMode(DetailsViewMode.Edit);
        DetailsView1.DataSource = table;
        DetailsView1.DataBind();
    }
    if (e.CommandName == "btnCancel")
    {
        DetailsView1.ChangeMode(DetailsViewMode.ReadOnly);
        DetailsView1.DataSource = table;
        DetailsView1.DataBind();
    }
}

}

1 个答案:

答案 0 :(得分：0)

我认为对我来说最大的问题是你的代码在你的语法中假设row.Cells[i].Controls。您应该检查以确保单元格具有“控件”集合。

看看这段代码，我的初始传感器变得疯狂。

if (e.CommandName == "btnSave")
{
    int j = 0;
    foreach (DetailsViewRow row in DetailsView1.Rows)
    {
        for (int i = 0; i < row.Cells.Count; i++)
        {
            TextBox tb = FindControl<TextBox>(row.Cells[i].Controls);
            if (tb != null)
            {
                table.Rows[0][j] = tb.Text;
            }

            CheckBox cb = FindControl<CheckBox>(row.Cells[i].Controls);
            if (cb != null)
            {
                table.Rows[0][j] = cb.Checked;
            }
        }
        j++;
    }

你上面所做的，实质上是将一个类型的变量'int'初始化为0（int j = 0;），但是你增加它，而不考虑你以后试图访问的列集合索引上面的代码，table.Rows[0][j] = cb.Checked;代表'DetailsView1.Rows'的每一行。

所以基本上你正在做的是在DetailsView1.Rows中每行递增1，并试图通过该索引访问DataTable的'Columns'。但是，如果该索引中不存在列，该怎么办？

我建议在过渡期间解决问题的一件事是在使用之前检查“Cells”集合中是否存在单元格。像这样...... 

if (table.Rows[0][j] != null)
{
    table.Rows[0][j] = tb.Text;
}

这只是一个乐队援助修复，不应该长期使用，因为可能迭代超过集合范围的根本问题不是真正可以接受的实践。我需要一些时间来分析你的方法和重构。是的，对于您来说，单元格应该全部存在可能是有意义的，因为您的详细信息视图的行数小于DataTable的单元格，但它仍然不是很好的做法，并且可能是您在此处出错的原因。

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