You have two problems here. The first is that the GUI thread is not responsive while copying large files. You should use a background thread to solve that, as others have suggested.
The other problem is that your current file copying routine does not support a progress callback function. The accepted answer to the question below has the information you need to write your own solution:
Can I show file copy progress using FileInfo.CopyTo() in .NET?
EDIT:
I just found this wrapper class for CopyFileEx. I tested it and it works great!
using System;
using System.ComponentModel;
using System.IO;
using System.Runtime.InteropServices;
using System.Security;
using System.Security.Permissions;
namespace FileCopyTest {
public sealed class FileRoutines {
public static void CopyFile(FileInfo source, FileInfo destination) {
CopyFile(source, destination, CopyFileOptions.None);
}
public static void CopyFile(FileInfo source, FileInfo destination,
CopyFileOptions options) {
CopyFile(source, destination, options, null);
}
public static void CopyFile(FileInfo source, FileInfo destination,
CopyFileOptions options, CopyFileCallback callback) {
CopyFile(source, destination, options, callback, null);
}
public static void CopyFile(FileInfo source, FileInfo destination,
CopyFileOptions options, CopyFileCallback callback, object state) {
if (source == null) throw new ArgumentNullException("source");
if (destination == null)
throw new ArgumentNullException("destination");
if ((options & ~CopyFileOptions.All) != 0)
throw new ArgumentOutOfRangeException("options");
new FileIOPermission(
FileIOPermissionAccess.Read, source.FullName).Demand();
new FileIOPermission(
FileIOPermissionAccess.Write, destination.FullName).Demand();
CopyProgressRoutine cpr = callback == null ?
null : new CopyProgressRoutine(new CopyProgressData(
source, destination, callback, state).CallbackHandler);
bool cancel = false;
if (!CopyFileEx(source.FullName, destination.FullName, cpr,
IntPtr.Zero, ref cancel, (int)options)) {
throw new IOException(new Win32Exception().Message);
}
}
private class CopyProgressData {
private FileInfo _source = null;
private FileInfo _destination = null;
private CopyFileCallback _callback = null;
private object _state = null;
public CopyProgressData(FileInfo source, FileInfo destination,
CopyFileCallback callback, object state) {
_source = source;
_destination = destination;
_callback = callback;
_state = state;
}
public int CallbackHandler(
long totalFileSize, long totalBytesTransferred,
long streamSize, long streamBytesTransferred,
int streamNumber, int callbackReason,
IntPtr sourceFile, IntPtr destinationFile, IntPtr data) {
return (int)_callback(_source, _destination, _state,
totalFileSize, totalBytesTransferred);
}
}
private delegate int CopyProgressRoutine(
long totalFileSize, long TotalBytesTransferred, long streamSize,
long streamBytesTransferred, int streamNumber, int callbackReason,
IntPtr sourceFile, IntPtr destinationFile, IntPtr data);
[SuppressUnmanagedCodeSecurity]
[DllImport("Kernel32.dll", CharSet = CharSet.Auto, SetLastError = true)]
private static extern bool CopyFileEx(
string lpExistingFileName, string lpNewFileName,
CopyProgressRoutine lpProgressRoutine,
IntPtr lpData, ref bool pbCancel, int dwCopyFlags);
}
public delegate CopyFileCallbackAction CopyFileCallback(
FileInfo source, FileInfo destination, object state,
long totalFileSize, long totalBytesTransferred);
public enum CopyFileCallbackAction {
Continue = 0,
Cancel = 1,
Stop = 2,
Quiet = 3
}
[Flags]
public enum CopyFileOptions {
None = 0x0,
FailIfDestinationExists = 0x1,
Restartable = 0x2,
AllowDecryptedDestination = 0x8,
All = FailIfDestinationExists | Restartable | AllowDecryptedDestination
}
}
