VB -- How does the "Using" statement translate from C# to VB?

Question

For example:

BitmapImage bitmap = new BitmapImage();

byte[] buffer = GetHugeByteArray(); // from some external source
using (MemoryStream stream = new MemoryStream(buffer, false))
{
    bitmap.BeginInit();
    bitmap.CacheOption = BitmapCacheOption.OnLoad;
    bitmap.StreamSource = stream;
    bitmap.EndInit();
    bitmap.Freeze();
}

Can you tell me any more about "using"? (Trying to find out about a word as ambiguous as "using" is pretty fruitless on google.)

Answer 1

Using has virtually the same syntax in VB as C#, assuming you're using .NET 2.0 or later (which implies the VB.NET v8 compiler or later). Just remove the braces and add a "End Using"

Dim bitmap as New BitmapImage()
Dim buffer As Byte() = GetHugeByteArrayFromExternalSource()
Using stream As New MemoryStream(buffer, false))
    bitmap.BeginInit()
    bitmap.CacheOption = BitmapCacheOption.OnLoad
    bitmap.StreamSource = stream
    bitmap.EndInit()
    bitmap.Freeze()
End Using

You can get the full documentation here

• http://msdn.microsoft.com/en-us/library/htd05whh(VS.80).aspx

EDIT

If you're using VS2003 or earlier you'll need the below code. The using statement was not introduced until VS 2005, .NET 2.0 (reference). Thanks Chris!. The following is equivalent to the using statement.

Dim bitmap as New BitmapImage()
Dim buffer As Byte() = GetHugeByteArrayFromExternalSource()
Dim stream As New MemoryStream(buffer, false))
Try
    bitmap.BeginInit()
    bitmap.CacheOption = BitmapCacheOption.OnLoad
    bitmap.StreamSource = stream
    bitmap.EndInit()
    bitmap.Freeze()
Finally
    DirectCast(stream, IDisposable).Dispose()
End Try

Answer 2

That would be something like this:

Dim bitmap As New BitmapImage()
Dim buffer As Byte() = GetHugeByteArray()
Using stream As New MemoryStream(buffer, False)
    bitmap.BeginInit()
    bitmap.CacheOption = BitmapCacheOption.OnLoad
    bitmap.StreamSource = stream
    bitmap.EndInit()
    bitmap.Freeze()
End Using

Answer 3

See http://www.harding.edu/fmccown/vbnet_csharp_comparison.html#strings for a quite decent comparison of the 2, including your question.

Answer 4

The key point is that the class being "used" must implement the IDisposable interface.

Answer 5

Its important to point out that using is actually compiled into various lines of code, similar to lock, etc.

From the C# language specification.... A using statement of the form

using (ResourceType resource = expression) statement

corresponds to one of two possible expansions. When ResourceType is a value type, the expansion is

{
    ResourceType resource = expression;
    try {
     statement;
    }
    finally {
     ((IDisposable)resource).Dispose();
    }
}

Otherwise, when ResourceType is a reference type, the expansion is

{
    ResourceType resource = expression;
    try {
     statement;
    }
    finally {
     if (resource != null) ((IDisposable)resource).Dispose();
    }
}

(end language specification snippet)

Basically, at compile time its converted into that code. There is no method called using, etc. I tried to find similar stuff in the vb.net language specification but I couldn't find anything, presumably it does the exact same thing.

Answer 6

These guys are very good at the vb <- > c# conversion

http://converter.telerik.com/