编译器警告：空引用异常

我在 Visual Studio 2005 中有以下代码。

    Dim OutFile As System.IO.StreamWriter
    Try
        OutFile = New System.IO.StreamWriter(Filename)
       // Do stuff with OutFile
    Catch Ex As Exception
       // Handle Exception
    Finally
       If OutFile IsNot Nothing Then OutFile.Close()
    End Try

但是 VS2005 会出现“If OutFile IsNot..”这一行的警告

变量“OutFile”在赋值之前使用。运行时可能会导致空引用异常。

是否有某种方法可以通过巧妙地更改代码来消除此警告，或者是否有更好的方法来完成我想做的事情？

Thanks

Rob

Dim OutFile As System.IO.StreamWriter
OutFile = Nothing
Try
    OutFile = New System.IO.StreamWriter(Filename)
   // Do stuff with OutFile
Catch Ex As Exception
   // Handle Exception
Finally
   If OutFile IsNot Nothing Then OutFile.Close()
End Try

如同C# 错误：使用未分配的局部变量