void y_Click(object sender, RoutedEventArgs e)
{
CheckBox che = lbox.SelectedItem as CheckBox;
if ((bool)che.IsChecked)
{
MessageBox.Show(che.Content.ToString());
}
}
Here the button name is y and lbox is the listbox where I have added checkboxes dynamically.The button y is also added through Dynamically to the listbox.
这里的按钮名称为y，lbox是我已动态添加复选框的列表框。按钮y也通过动态添加到列表框中。
For button click event in the above code it says NullReferenceException and lbox.SelectedItem is Null as seen by breakpoint..If I implement the same code in lboxSelectionChanged event it works fine and lbox.SelectedItem is not null..
对于上面代码中的按钮单击事件，它说NullReferenceException和lbox.SelectedItem是断点所见的Null。如果我在lboxSelectionChanged事件中实现相同的代码，它工作正常，lbox.SelectedItem不为null。
What is wrong in my implementation?
我的实施有什么问题？
2 个解决方案
#1
3
If the as operator fails to cast to your desired type, it returns null. Most likely what is happening here is that your lbox.SelectedItem is not a CheckBox, or it is null. You should check that che is null before attempting to get its IsChecked property.
如果as运算符无法转换为所需类型，则返回null。很可能这里发生的是你的lbox.SelectedItem不是CheckBox，或者它是null。在尝试获取其IsChecked属性之前，您应该检查che是否为null。
void y_Click(object sender, RoutedEventArgs e)
{
CheckBox che = lbox.SelectedItem as CheckBox;
if (che == null) return; // <--- Add this
if ((bool)che.IsChecked)
{
MessageBox.Show(che.Content.ToString());
}
}
#2
0
The thing actually is IsChecked is different from selectionchanged event of listbox.The checking of a checkbox doesn't mean that a listbox selection has been made. And the thing I found is that whenever I click on a checkbox content, the selection is changed but not when the checkbox is checked. So, that's the thing.
事实上IsChecked与listbox的selectionchanged事件不同。复选框的检查并不意味着已经进行了列表框选择。我发现的是，无论何时单击复选框内容，选中都会更改，但选中复选框时则不会更改。那就是那件事。
#1
3
If the as operator fails to cast to your desired type, it returns null. Most likely what is happening here is that your lbox.SelectedItem is not a CheckBox, or it is null. You should check that che is null before attempting to get its IsChecked property.
如果as运算符无法转换为所需类型，则返回null。很可能这里发生的是你的lbox.SelectedItem不是CheckBox，或者它是null。在尝试获取其IsChecked属性之前，您应该检查che是否为null。
void y_Click(object sender, RoutedEventArgs e)
{
CheckBox che = lbox.SelectedItem as CheckBox;
if (che == null) return; // <--- Add this
if ((bool)che.IsChecked)
{
MessageBox.Show(che.Content.ToString());
}
}
#2
0
The thing actually is IsChecked is different from selectionchanged event of listbox.The checking of a checkbox doesn't mean that a listbox selection has been made. And the thing I found is that whenever I click on a checkbox content, the selection is changed but not when the checkbox is checked. So, that's the thing.
事实上IsChecked与listbox的selectionchanged事件不同。复选框的检查并不意味着已经进行了列表框选择。我发现的是，无论何时单击复选框内容，选中都会更改，但选中复选框时则不会更改。那就是那件事。