Question

The following code works fine in C#.

    Int32 a, b;
    Int16 c;

    a = 0x7FFFFFFF;
    b = a & 0xFFFF;
    c = (Int16)b;

But this code crash with a OverflowException in VB.NET.

    Dim a, b As Int32
    Dim c As Int16

    a = &H7FFFFFFF
    b = a And &HFFFF
    c = CType(b, Int16)

Both code snippets seem the same to me. What is the difference and how can I get the C# code converted to VB.NET?

Answer 1

From MSDN:

For the arithmetic, casting, or conversion operation to throw an OverflowException, the operation must occur in a checked context. By default, arithmetic operations and overflows in Visual Basic are checked; in C#, they are not. If the operation occurs in an unchecked context, the result is truncated by discarding any high-order bits that do not fit into the destination type.

EDIT:
If you’re going to port code from C# to VB.NET, you may be interested in differences between them. Also compare and explicitly set compiler settings to be the same as default settings in C# (when needed).