String implementation in .NET Framework

J4amieC

I have some legacy VB6 code which im converting over to C#, and it seems that strings were implemented very differently in old VB than in the Framework. I get vastly different results from the ported code than I do from an app written in VB and I was wondering if anyone could put their finger on the reason why? here is the old VB code (pstrResponse is the input to the method):

For i = 1 To Len(pstrResponse)

  j = Asc(Mid(pstrResponse, i, 1))

  If j > 127 Then

     j = j - 128

     Mid(pstrResponse, i, 1) = Chr(j)

  End If

Next i

Here is my ported C# (input is the input):

char[] charArray = input.ToCharArray();
int bit;
for (int i = 0; i < charArray.Length; i++)
{
bit = (int)charArray[i];
if (bit > 127)
{
bit -= 128;
charArray[i] = (char)bit;
}
}
return new string(charArray);

As you can see, simple code & easy to port but very different results. Any ideas people?

Ennis Ray Lynch Jr

.NET stores string in Unicode not Ascii and a char is 2 bytes not one I think? Which would mean the -=128 could have a different value in an integer data type? I don't really know I am just speculating.

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J4amieC

Ennis Ray Lynch, Jr. wrote:

Which would mean the -=128 could have a different value in an integer data type

Any idea what it could be?

Ennis Ray Lynch Jr

Maybe, Asc(Mid(pstrResponse, i, 1)) != (int)characters[i]; Try using the System.Text.AsciiEncoder to change the string by ascii bytes only first and see what happens?

Need software developed? Offering C# development all over the United States, ERL GLOBAL, Inc is the only call you will have to make.
Happiness in intelligent people is the rarest thing I know. -- Ernest Hemingway
Most of this sig is for Google, not ego.

DaveyM69

Apparently this still exists in the Microsoft.VisualBasic namespace. This is the Asc function after being run through reflector - it seems to work OK.

public static int Asc(char theChar)
{
    int num;
    int num2 = Convert.ToInt32(theChar);
    if (num2 < 0x80)
    {
        return num2;
    }
    try
    {
        byte\[\] buffer;
        Encoding fileIOEncoding = Encoding.Default;
        char\[\] chars = new char\[\] { theChar };
        if (fileIOEncoding.IsSingleByte)
        {
            buffer = new byte\[1\];
            int num3 = fileIOEncoding.GetBytes(chars, 0, 1, buffer,
            0);
            return buffer\[0\];
        }
        buffer = new byte\[2\];
        if (fileIOEncoding.GetBytes(chars, 0, 1, buffer, 0) == 1)
        {
            return buffer\[0\];
        }
        if (BitConverter.IsLittleEndian)
        {
            byte num4 = buffer\[0\];
            buffer\[0\] = buffer\[1\];
            buffer\[1\] = num4;
        }
        num = BitConverter.ToInt16(buffer, 0);
    }
    catch (Exception exception)
    {
        throw exception;
    }
    return num;
}

Dave
BTW, in software, hope and pray is not a viable strategy. (Luc Pattyn)
Visual Basic is not used by normal people so we're not covering it here. (Uncyclopedia)

PIEBALDconsult

J4amieC wrote:

As you can see, simple code & easy to port but very different results

No, I can't see; what are the results? Provided you don't care about Unicode, you could use: System.Text.Encoding.ASCII.GetBytes() and System.Text.Encoding.ASCII.GetString() You could also access the characters in an unsafe context much like your VB code. Something like:

private unsafe static void
ASCIIize
(
string Subject
)
{
fixed ( char* subject = Subject )
{
int* length = (int*) subject - 1 ;
int index = 0 ;

    while ( index < \*length )
    {
        \*(subject + index) &= (char) 0x7F ;

        index++ ;
    }
}

return ;

}

(Though I haven't tested this with the problematic characters.)

J4amieC

Thanks for the pointers. With your help ive managed to solve the problem, but strangly enough I thought id need to convert my input to ASCII using ASCIIEncoding.GetBytes. In actual fact I had to use DefaultEncoding.GetBytes to get the result I was expecting. :confused: here's the working code now:

byte[] byteArray = Encoding.Default.GetBytes(input);

StringBuilder sb = new StringBuilder(byteArray.Length);
byte bit;
for (int i = 0; i < byteArray.Length; i++)
{
bit = (byte)byteArray[i];
if (bit > 127)
{
bit -= 128;
}
sb.Append((char)bit);
}
return sb.ToString();

Thanks again for your help.

J4amieC

Yeah, I saw that but I was attempting to avoid the use of nasty VB namespaces X|

J4amieC

PIEBALDconsult wrote:

No, I can't see; what are the results?

The results are cryptic, horrible and mostly non-printable characters which is why I didnt post them. I meant the code was easy enough to port on the face of it.

DaveyM69

J4amieC wrote:

nasty VB

:laugh: If you use the code above you don't need to - it's just that function converted to C#

Dave
BTW, in software, hope and pray is not a viable strategy. (Luc Pattyn)
Visual Basic is not used by normal people so we're not covering it here. (Uncyclopedia)