Newbie struggling with a simple program?

See if this will fix the file access problem:

1. add this to your app's 'using statements:

using System.Security.Permissions;

2. add this Attribute just above the method(s) where you are getting access denied errors now:

[PermissionSet(SecurityAction.Demand, Name = "FullTrust")]
private void MyFileAccessMethod(?,?,?)
{
}

Several points of confusion here:

1) Path.GetFullPath(xmlFile.Name) will combine the name of the XML file with the current working directory. That will not be the same as the full path of the XML file, which you can retrieve using xmlFile.FullName;

2) You don't actually want the full path of the XML file; since you're trying to copy other files to the path, you want the path of the parent directory. You can retrieve that using xmlFile.DirectoryName;

3) Since tifLoc is a directory, you can't use File.Copy to copy it elsewhere. Unfortunately, you need to copy the individual files separately.

4) Directory.GetDirectories(...).FirstOrDefault() will return null if the directory doesn't exist. In that case, you'll get a NullReferenceException on the next line, when you try to call .ToString() on the returned string value.

Also, you'll probably want to use EnumerateFiles and EnumerateDirectories instead of their Get* counterparts, particularly if there are a lot of files to process. The Get* versions have to load all matches into memory before you can start processing them, whereas the Enumerate* versions let you start processing as soon as the first match is found.

Something like this should work:

DirectoryInfo diCopyFrom = new DirectoryInfo(textBox1.Text);
DirectoryInfo diCopyTo = new DirectoryInfo(textBox2.Text);

foreach (FileInfo xmlFile in diCopyTo.EnumerateFiles("*.xml", SearchOption.AllDirectories))
{
    // Eg:
    // xmlFile = "E:\Jobs\12334-12366\1\xml\12345.xml"
    
    string tifDirectoryName = Path.GetFileNameWithoutExtension(xmlFile.Name);
    // tifDirectoryName = "12345"
    
    DirectoryInfo sourceDirectory = diCopyFrom.EnumerateDirectories(tifDirectoryName, SearchOption.AllDirectories).FirstOrDefault();
    if (sourceDirectory != null)
    {
        string destinationDirectoryName = xmlFile.DirectoryName;
        // destinationDirectoryName = "E:\Jobs\12334-12366\1\xml\"
        
        foreach (FileInfo tifFile in sourceDirectory.EnumerateFiles("*.tif"))
        {
            // tifFile = "D:\database\12345\tiffile1.tif"
            
            string destFileName = Path.Combine(destinationDirectoryName, tifFile.Name);
            // destFileName = "E:\Jobs\12334-12366\1\xml\tiffile1.tif"
            
            tifFile.CopyTo(destFileName, true);
        }
    }
}