How to use StructLayoutAttribute and MarshalAsAttribute

[VenkatRastapuram]

Hello Sir,

I am sending a sample code which is used to search for a file by importing kernel32.dll. But in the sample code it is unable to comile. It is giving two compilation errors saying that StructLayoutAttribute does not contain a definition for CharSet and another one is the type or namespace name MarshalAs could not be found. How to solve this problem.

using System;
using System.Text;
using System.Runtime.InteropServices;

// Declares a class member for structure element.
[ StructLayout( LayoutKind.Sequential, CharSet=CharSet.Auto )]

public class FindData
{
public int fileAttributes = 0;
// creationTime was an embedded FILETIME structure.
public int creationTime_lowDateTime = 0 ;
public int creationTime_highDateTime = 0;
// lastAccessTime was an embedded FILETIME structure.
public int lastAccessTime_lowDateTime = 0;
public int lastAccessTime_highDateTime = 0;
// lastWriteTime was an embedded FILETIME structure.
public int lastWriteTime_lowDateTime = 0;
public int lastWriteTime_highDateTime = 0;
public int nFileSizeHigh = 0;
public int nFileSizeLow = 0;
public int dwReserved0 = 0;
public int dwReserved1 = 0;
[ MarshalAs( UnmanagedType.ByValTStr, SizeConst=256 )]
public String fileName = null;
[ MarshalAs( UnmanagedType.ByValTStr, SizeConst=14 )]
public String alternateFileName = null;
}


public class LibWrap

{

// Declares a managed prototype for the unmanaged function.
[DllImport( "Kernel32.dll", CharSet=CharSet.Auto )]
public static extern IntPtr FindFirstFile( String fileName, [ In, Out ]
FindData findFileData );


[ DllImport( "Kernel32.dll", CharSet=CharSet.Auto )]

public static extern int FindNextFile( IntPtr handle, ref FindData

findFileData );

}

Thanking U

Regards,
R.Venatesh
MakeLogic

http://www.makelogic.com

venkat@makelogicmldb.com

 

[obislavu]

I did copy/paste of your code and it is working.
Maybe there is something when you use that code.
I did like here:

private void btnFindFile_Click(object sender, System.EventArgs e)
{   	string strFileName="C:\\aup.txt";
	FindData fd = new FindData();
	IntPtr h =LibWrap.FindFirstFile (strFileName,fd);
	if (h != IntPtr.Zero)
	{
		LibWrap.FindNextFile(h, ref fd);
		//FindData fd2 = (FindData)Marshal.PtrToStructure(h,fd.GetType());
	}
	if (fd.fileName.Length >0)
	{
		System.Windows.Forms.MessageBox.Show("Found file " +fd.fileName);
	}
	else
	{
		System.Windows.Forms.MessageBox.Show("File doesn't exist");
	}

}

obislavu

 

[VenkatRastapuram]

Hi Obislavu ,

Thank you for your response.

I think u have selecte the application as a windows application. In the windows application it is working properly but when I copy the same code in the Smart device application it is giving comilation errors. So please tell me how to invoke the methods in the smart device application.

Thanking U

Regards,
R.Venkatesh
MakeLogic

http://www.makelogic.com

venkat@makelogicmldb.com

 

[obislavu]

Sorry, I don't know why is not working on the Smart device.
obislavu