Equivalent of "Unchecked" keyword \expression in VB.NET

Question

Hi,

I have converted the following C# code to VB.NET.But I am unable to find the equivalent of C# "Unchecked" keyword in VB.NET.Below is the C# Code and following the C# Code is converted VB Code.After conversion and building the VB Code I am getting the error :   "Constant expression not representable in type 'UInteger'."

C#:

if (milliseconds == unchecked((uint)Timeout.Infinite))
            {
                return TimeSpan.MaxValue;
            }

Converted VB.NET:

If milliseconds = (CUInt(System.Threading.Timeout.Infinite)) Then
                Return System.TimeSpan.MaxValue
            End if

Please help me out ASAP.

Thanks,

Vipin

Answer 1

          try this -

          if (milliseconds == ((uint)System.Threading.Timeout.Infinite))
                {
                    return System.TimeSpan.MaxValue;
                }

 

jayant

http://www.3acesnetwork.blogspot.com/

Answer 2

Hi Jayant,

 

Thanks...But this is for C#...i want it in VB.Net.

 

Waiting..

Answer 3

ok just remove threading

try this

If milliseconds = CUInt(Timeout.Infinite) Then
        Return TimeSpan.MaxValue
End If

and inform me it is working or not.

 

jayant

Answer 4

if  above code is not  working then

try this.

If milliseconds = Convert.ToUInt16(Timeout.Infinite) Then
        Return TimeSpan.MaxValue
End If

 

jayant

Answer 5

Hi Jayant,

I tried this....but on 'Timeout.Infinite' it's giving error 'Constant expression not representable in type 'UInteger'

 

 

 

If milliseconds = CUInt(Timeout.Infinite) Then

Return TimeSpan.MaxValue

End If

 

 

 

 Plz let me know...

Answer 6

try this.

If milliseconds = Convert.ToUInt16(Timeout.Infinite) Then
        Return TimeSpan.MaxValue
End If

 

jayant

Answer 7

Hi,

 

For your information,below is the actual complete function in C# to be converted to VB.Net

public static TimeSpan FromMilliseconds(uint milliseconds)
        {
            if (milliseconds == unchecked((uint)Timeout.Infinite))
            {
                return TimeSpan.MaxValue;
            }
            else
            {
                return TimeSpan.FromMilliseconds(milliseconds);
            }
        }

...Thanks..Waiting...

Answer 8

Your C# code is just a bit out of context.  Please post the entire method. 

The original code is not making sense.  It is casting a 32-bit integer constant to an an unsigned 32-bit integer. The value of the constant is -1.  What is the point in cast an integer constant that will always thrown an exception?  The code generates the following compiler warning.

" Warning - Comparison to integral constant is useless; the constant is outside the range of type 'int' "

The unchecked keyword in C# is used to disable run time exceptions being thrown on integer overflows when performing calculations.  There are some circumstances where the overflow is of no concern.  This ain't one of them.   

There is no direct equivalent keyword in Visual Basic.  In VB you must perform the risky calculation inside of a Try/Catch/Finally block.

Rudy  =8^D

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Mark the best replies as answers. "Fooling computers since 1971."

Answer 9

Hi Vipins,

I would not worry about the keyword unchecked from C# in this scenario as you are not attempting to change the value

passed to the Function, within the Function itself .  :-)

 

As forum user Rudy a.k.a. RudeDog2 has said, there is no equivalent in Vb.Net.

 

The constant System.Threading.Timeout.Infinite has a value of -1 according to.>>

http://msdn.microsoft.com/en-us/library/system.threading.timeout.infinite (VS.85).aspx

so using a UInt or unsigned Integer of any size does not make any sense as they all have a minimum value = 0

 

Anyway, I believe C# Public Static equates to a Public Shared method in Vb.Net so my best attempt at conversion

and writing a Function that should not create an error is ( I added an overloaded version in case you want to pass a negative Integer).>>

 

 

    Public Shared Function FromMilliseconds(ByVal milliSeconds As UInteger) As TimeSpan

        If milliSeconds = System.Threading.Timeout.Infinite Then
            Return TimeSpan.MaxValue
        ElseIf milliSeconds >= 0 And milliSeconds <= TimeSpan.MaxValue.TotalMilliseconds Then
            Return TimeSpan.FromMilliseconds(milliSeconds)
        End If

    End Function

    'Overloaded version in case you want to pass a negative value.>>
    Public Shared Function FromMilliseconds(ByVal milliSeconds As Integer) As TimeSpan

        If milliSeconds = System.Threading.Timeout.Infinite Then
            Return TimeSpan.MaxValue
        ElseIf milliSeconds >= TimeSpan.MinValue.TotalMilliseconds And milliSeconds <= TimeSpan.MaxValue.TotalMilliseconds Then
            Return TimeSpan.FromMilliseconds(milliSeconds)
        End If

    End Function

 

 

Regards,

John

 

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Please see this thread for Vb.Net learning links.>> http://social.msdn.microsoft.com/Forums/en/vbgeneral/thread/549c8895-6780-42f8-878f-2138214fdeb4

Answer 10

Check this option, not exact what you are trying but related

http://msdn.microsoft.com/en-us/library/key2x70f(VS.71).aspx

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Arjun Paudel

Answer 11

Check this option, not exact what you are trying but related

http://msdn.microsoft.com/en-us/library/key2x70f(VS.71).aspx

---

Arjun Paudel

 

Excellent suggestion. 

Be aware of the primary difference between this option and the C# keyword.  This option will apply to the entire assembly, while the keyword applies to just the block of code that it surrounds.

The keyword is used when the remainder from the overflow is of interest.

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Mark the best replies as answers. "Fooling computers since 1971."

Answer 12

i see that no one really answered your question correctly. i had a similar question and here's what i found. VB and C# both let you set the entire project as checking for overflow or not checking for overflow. But that's not what i was looking for. Vipins in your case, you just need to know what C# does with -1 when converting to an unsigned value: the Max Unsigned value is the result. So your equivalent VB code If statement would be:

' System.Threading.Timeout.Infinite = -1, so its UInt32 equivalent = UInt32.MaxValue

If milliseconds = UInt32.MaxValue Then Return System.TimeSpan.MaxValue

It is that simple. When converting C# `checked` or `unchecked` keywords to VB.NET, if you still want simple and clean VB.NET code, then you really need to realize what is happening and recode it a bit differently. But you can always use a larger int datatype and then truncate the int down to the size you want. Or you can use BitConverter to convert one value to Bytes then back to the int type that you want. The BitConverter type would look like this:

If milliseconds = BitConverter.ToUInt32(BitConverter.GetBytes(System.Threading.Timeout.Infinite), 0) Then Return System.TimeSpan.MaxValue

Personally, i prefer the first snippet. But suit yourself.

Answer 13

i see that no one really answered your question correctly. i had a similar question and here's what i found. VB and C# both let you set the entire project as checking for overflow or not checking for overflow. But that's not what i was looking for. Vipins in your case, you just need to know what C# does with -1 when converting to an unsigned value: the Max Unsigned value is the result. So your equivalent VB code If statement would be:

' System.Threading.Timeout.Infinite = -1, so its UInt32 equivalent = UInt32.MaxValue

If milliseconds = UInt32.MaxValue Then Return System.TimeSpan.MaxValue

It is that simple. When converting C# `checked` or `unchecked` keywords to VB.NET, if you still want simple and clean VB.NET code, then you really need to realize what is happening and recode it a bit differently. But you can always use a larger int datatype and then truncate the int down to the size you want. Or you can use BitConverter to convert one value to Bytes then back to the int type that you want. The BitConverter type would look like this:

If milliseconds = BitConverter.ToUInt32(BitConverter.GetBytes(System.Threading.Timeout.Infinite), 0) Then Return System.TimeSpan.MaxValue

Personally, i prefer the first snippet. But suit yourself.

Hello, be aware that this thread is five years old and nobody has asked this question in a very long time. Best to answer questions that are 30 days old or less.

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