Comparing a null terminated string to a non-null terminated string

Question

I pulling image tags from a directory of images using System.Drawing.Imaging. I can pull the tags just fine, but the problem is the string coming off the PropertyItem is null terminated but the string I'm comparing it to is not. My question is, how do I compare a null terminated string to a non-null terminated string in C#?

Here is the code I'm running

byte[] tagBytes = new byte[tag.Length * sizeof(char)];
System.Buffer.BlockCopy(tag.ToCharArray(), 0, tagBytes, 0, tagBytes.Length);

pnl_slider.Visible = false;
string relativePath = ConfigurationManager.AppSettings["PhotoPathRelative"];
DirectoryInfo info = new DirectoryInfo(ConfigurationManager.AppSettings["PhotoPathPhysical"]);
FileInfo[] Files = info.GetFiles("*.jpg").OrderBy(p => p.CreationTime).ToArray();
foreach (FileInfo file in Files)
{
    System.Drawing.Image img = new Bitmap(file.FullName);
    foreach (PropertyItem item in img.PropertyItems)
    {
        if (item.Id == 40094)
        {
            str += "'" + Encoding.Unicode.GetString(item.Value).Trim() + "' " + BitConverter.ToString(item.Value) + " == " + BitConverter.ToString(tagBytes) + "<br/>";
        }
    }
    img.Dispose();
}

The output of 'str' looks something like this:

'wildlife' 77-00-69-00-6C-00-64-00-6C-00-69-00-66-00-65-00-00-00 == 77-00-69-00-6C-00-64-00-6C-00-69-00-66-00-65-00
'wildlife' 77-00-69-00-6C-00-64-00-6C-00-69-00-66-00-65-00-00-00 == 77-00-69-00-6C-00-64-00-6C-00-69-00-66-00-65-00
'wildlife' 77-00-69-00-6C-00-64-00-6C-00-69-00-66-00-65-00-00-00 == 77-00-69-00-6C-00-64-00-6C-00-69-00-66-00-65-00
'macro' 6D-00-61-00-63-00-72-00-6F-00-00-00 == 77-00-69-00-6C-00-64-00-6C-00-69-00-66-00-65-00

just call Encoding.Unicode.GetString(item.Value).Trim() on the byte arrays, the output string should be the same, you see in the output the last 00-00 has been stripped by the decoder. — kennyzx
– kennyzx, Commented Nov 25, 2014 at 3:33
@kennyzx I gave it a try and no dice, same issue. if(Encoding.Unicode.GetString(item.Value).Trim() == Encoding.Unicode.GetString(tagBytes).Trim()) — Chris Stillwell
– Chris Stillwell, Commented Nov 25, 2014 at 3:42
Looks like you have to trim the terminator manually, I thought this was done by the decoder but I was wrong. — kennyzx
– kennyzx, Commented Nov 25, 2014 at 4:07

Community · Accepted Answer · 2017-05-23 11:58:11Z

0

Trimming the nulls manually did the trick as shown in this answer:

Getting null terminated string from System.Text.Encoding.Unicode.GetString

edited May 23, 2017 at 11:58

CommunityBot

11 silver badge

answered May 29, 2015 at 21:03

Chris Stillwell

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