Question

编辑：这不是一个重复的问题，因为我的问题比简单的NullReferenceException更复杂。

这是给我一些问题的代码：

 private void BindData()
{
    SqlConnection con = new SqlConnection(Connection.constr);
    con.Open();
    string[] Querys = new string[4];
    Querys[0] = "PopulateConstraintTable";
    Querys[1] = "PopulateModuleTable";
    Querys[2] = "PopulateFeatureTable";
    Querys[3] = "PopulateInterfaceTable";
    for (int n = 0; n < 4; n++)
    {
        SqlCommand cmd = new SqlCommand(Querys[n], con);
        cmd.CommandType = CommandType.StoredProcedure;
        cmd.Parameters.Add("@License", SqlDbType.Int).Value = 20000 + MyGlobals.CurrentOrgID;
        SqlDataAdapter da = new SqlDataAdapter(cmd);
        DataTable Table = new DataTable();
        da.Fill(Table);
        ((GridView)Page.FindControl("GridView" + (n + 1))).DataSource = Table;
        ((GridView)Page.FindControl("GridView" + (n + 1))).DataBind();
        cmd.ExecuteNonQuery();
    }
    con.Close();
}

此代码应该使用这些存储过程中的信息填充4个不同的Gridview，但是我在行中出现错误

 ((GridView)Page.FindControl("GridView" + (n + 1))).DataSource = Table;
 ((GridView)Page.FindControl("GridView" + (n + 1))).DataBind();

说：

 An exception of type 'System.NullReferenceException' occurred in App_Web_30v1z0on.dll but was not handled in user code

 Additional information: Object reference not set to an instance of an object.

请问有人带我走错路吗？谢谢！

编辑：标记 -

<asp:GridView 
    ID="GridView1" 
    runat="server" 
    CellPadding="6" 
    GridLines="Horizontal"
    Font-Names="Verdana" 
    Font-Size="10pt" 
    DataKeyNames="ConstraintID" 
    AutoGenerateColumns="false" 
    allowpaging="false"
    Width="730px">

    <EditRowStyle BackColor="#999999" />
    <FooterStyle BackColor="#5D7B9D" Font-Bold="True" ForeColor="White" />
    <HeaderStyle BackColor="#5D7B9D" ForeColor="White" HorizontalAlign="Left" Height="25" Font-Bold="True" />   
    <AlternatingRowStyle BackColor="White" ForeColor="#284775" />

    <Columns>...</Columns>



    <PagerStyle BackColor="#284775" ForeColor="White" HorizontalAlign="Center" />
    <RowStyle BackColor="#F7F6F3" ForeColor="#333333" />
    <SelectedRowStyle BackColor="#E2DED6" Font-Bold="false" ForeColor="#333333" />
    <SortedAscendingCellStyle BackColor="#E9E7E2" />
    <SortedAscendingHeaderStyle BackColor="#506C8C" />
    <SortedDescendingCellStyle BackColor="#FFFDF8" />
    <SortedDescendingHeaderStyle BackColor="#6F8DAE" />

    </asp:GridView>

<asp:GridView 
    ID="GridView2" 
    cellpadding="6"
    runat="server" 
    GridLines="Horizontal"
    Font-Names="Verdana" 
    Font-Size="10pt" 
    DataKeyNames="ModuleID" 
    AutoGenerateColumns="False"
    onrowcancelingedit="GridView2_RowCancelingEdit" 
    onrowediting="GridView2_RowEditing" 
    onrowupdating="GridView2_RowUpdating" 
    Width="730px">


    <HeaderStyle BackColor="#336699" ForeColor="White" HorizontalAlign="Left" Height="25" />            

    <Columns>...</Columns>

</asp:GridView>


<asp:GridView 
    ID="GridView3" 
    runat="server" 
    CellPadding="6" 
    GridLines="Horizontal"
    Font-Names="Verdana" 
    Font-Size="10pt" 
    DataKeyNames="FeatureID" 
    AutoGenerateColumns="false" 
    allowpaging="false"
    onrowcancelingedit="GridView3_RowCancelingEdit" 
    onrowediting="GridView3_RowEditing" 
    onrowupdating="GridView3_RowUpdating" 
    OnRowDataBound="GridView3_RowDataBound"
    Width="730px">

    <EditRowStyle Font-Bold="True" />

    <HeaderStyle BackColor="#336699" ForeColor="White" HorizontalAlign="Left" Height="25" />   

    <Columns>...</Columns>
</asp:GridView>



<asp:GridView 
    ID="GridView4" 
    runat="server" 
    CellPadding="6" 
    GridLines="Horizontal"
    Font-Names="Verdana" 
    Font-Size="10pt" 
    DataKeyNames="InterfaceID" 
    AutoGenerateColumns="false" 
    allowpaging="false"
    onrowcancelingedit="GridView4_RowCancelingEdit" 
    onrowediting="GridView4_RowEditing" 
    onrowupdating="GridView4_RowUpdating" 
    OnRowDataBound="GridView4_RowDataBound"
    Width="730px">

    <EditRowStyle Font-Bold="True" />

    <HeaderStyle BackColor="#336699" ForeColor="White" HorizontalAlign="Left" Height="25" />   

    <Columns>...</Columns>
</asp:GridView>

答案： 看到这篇文章如何被人们轰炸声称这是一个副本，因此我无法发表答案，我将把答案放在编辑中（所有的荣誉和赞美都归@ConnorsFan所有）

解决方案是用

替换两个问题代码行

 ((GridView)Master.FindControl("MainContent").FindControl("GridView" + (n + 1))).DataSource = Table;
 ((GridView)Master.FindControl("MainContent").FindControl("GridView" + (n + 1))).DataBind();

Answer 1

这是空的，

Page.FindControl("GridView" + (n + 1))

您可以粘贴标记，以便我们检查它。

对象引用未设置为对象的实例（使用Gridviews）

1 个答案: