VB.NET中如何避免System.NullReferenceException异常？
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本文共计393个文字，预计阅读时间需要2分钟。
What is a NullReferenceException, and how do I fix it?I have a VB.NET program that can build multiple datasets from 10 different databases. I encountered this error: System.NullReferenceException: Object referenced not...
A NullReferenceException occurs when you try to access a property or method of an object that is null. This means the object does not exist or has not been initialized.
To fix it, you should:
1.Check if the object is null before accessing its properties or methods.
2.Initialize the object before using it.
3.Use the Is Nothing operator to check for null in VB.NET.
参见英文答案 > What is a NullReferenceException, and how do I fix it?31个我有一个VB.NET程序,可以从10个不同的数据库构建多个数据集.
我得到了这个例外：
System.NullReferenceException: Object referenced not set to an instance of an object:
此错误发生在以下行：
Me.OverTableAdapter.Adapter.SelectCommand.CommandTimeout = 60000 Me.OverTableAdapter.Fill(Me.Dataset.Over, TodayDt, TodayEnd)
这个例外意味着什么？
好吧,如果它在这条线上失败了：Me.OverTableAdapter.Adapter.SelectCommand.CommandTimeout = 60000
然后：
> Me.OverTableAdapter没什么
> Me.OverTableAdapter.Adapter没什么
> Me.OverTableAdapter.SelectCommand是Nothing
(你向我们展示的第二行是无关紧要的,因为你没有那么远.)
我们无法根据您向我们展示的内容进行分析,但您应该能够在调试器中或通过添加诊断日志记录来查找.
一旦你弄清楚它为什么会失败,修复它应该很容易 – 几乎可以肯定只是正确地初始化它.将此适配器的初始化与其他适配器的初始化进行比较.
本文共计393个文字，预计阅读时间需要2分钟。
What is a NullReferenceException, and how do I fix it?I have a VB.NET program that can build multiple datasets from 10 different databases. I encountered this error: System.NullReferenceException: Object referenced not...
A NullReferenceException occurs when you try to access a property or method of an object that is null. This means the object does not exist or has not been initialized.
To fix it, you should:
1.Check if the object is null before accessing its properties or methods.
2.Initialize the object before using it.
3.Use the Is Nothing operator to check for null in VB.NET.
参见英文答案 > What is a NullReferenceException, and how do I fix it?31个我有一个VB.NET程序,可以从10个不同的数据库构建多个数据集.
我得到了这个例外：
System.NullReferenceException: Object referenced not set to an instance of an object:
此错误发生在以下行：
Me.OverTableAdapter.Adapter.SelectCommand.CommandTimeout = 60000 Me.OverTableAdapter.Fill(Me.Dataset.Over, TodayDt, TodayEnd)
这个例外意味着什么？
好吧,如果它在这条线上失败了：Me.OverTableAdapter.Adapter.SelectCommand.CommandTimeout = 60000
然后：
> Me.OverTableAdapter没什么
> Me.OverTableAdapter.Adapter没什么
> Me.OverTableAdapter.SelectCommand是Nothing
(你向我们展示的第二行是无关紧要的,因为你没有那么远.)
我们无法根据您向我们展示的内容进行分析,但您应该能够在调试器中或通过添加诊断日志记录来查找.
一旦你弄清楚它为什么会失败,修复它应该很容易 – 几乎可以肯定只是正确地初始化它.将此适配器的初始化与其他适配器的初始化进行比较.