DataGrid MouseUp时，对象引用未设置...错误 [英] Object reference not set... error, when DataGrid MouseUp

问题描述

关于wpf Datagrid MouseUp事件，我用Google搜索但无法获取这是什么错误？我的片段如下：

About wpf Datagrid MouseUp event, I googled but can not get What's this error? My snippets as follow:

<DataGrid x:Name="gridTable1">
    <DataGrid.ItemContainerStyle>
        <Style TargetType="DataGridRow">
            <EventSetter Event="MouseUp" Handler="dataGridRow_MouseUp"/>
        </Style>
    </DataGrid.ItemContainerStyle>
</DataGrid>

Code Behind：

Code Behind:

private void dataGridRow_MouseUp(object sender, MouseButtonEventArgs e)
   {
       DataGridRow dgr = sender as DataGridRow;
       DataRowView drv = dgr.DataContext as DataRowView; //This error: Object reference not set to an instance of an object

       string requestId = drv.Row["RequestID"].ToString();

       DataTable dt = new DataTable();
       dt = db.MySelect("select RequestID from Requests where RequestID='" + requestId + "'");
       gridTable2.ItemsSource = dt.DefaultView;
   }

发生此错误：对象引用未设置为对象实例。

是否有任何代码示例？

This error occured: Object reference not set to an instance of an object.
Is there any code sample?

推荐答案

显然，发件人不是DataGridRow - 所以dgr得到一个null。

猜测，它是一个DataGrid，而不是一行 - 但是在调试器中查看它应该告诉你。

Clearly, the sender is not a DataGridRow - so dgr gets a null.
At a guess, it's a DataGrid, not a row - but look in the debugger and it should tell you.

对它的第100000000个回答问题...（当然不是你的错）



所以：

使用你的调试器！设置一个断点，看看什么是null。这是基本和必要的，没有其他方法（基本调试的知识）。

如果我不得不猜测，我会说你的DataContext不是DataRowView（看看怎么样 as 运算符的行为 - 如果对象不可转换则返回空引用）或者没有分配DataContext（不太可能）



我希望你能快速发现它，祝你的项目好运！

The 100000000th answer to the same question... (Not your fault of course)

So:
Use your Debugger! Set a breakpoint, have a look what's null. This is so basic and essential, there is no other way arround this (knowledge of basic debugging).
If I have to guess, I'd say your DataContext is not a DataRowView (have a look how the as operator behaves - it returns a null reference if the object is not convertible) or no DataContext is assigned (unlikely)

I hope you can spot it quickly, good luck with your Project!

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