A call to PInvoke function has unbalanced the stack. This is likely because the managed PInvoke .. (.NET 4)

Question

My project run successful without errors in .NET Frame work 3.5. But, When I target it to .NET Frame work 4. I got the error:

"A call to PInvoke function has unbalanced the stack. This is likely because the managed PInvoke signature does not match the unmanaged target signature."

I used unmanaged library as below:

[StructLayout(LayoutKind.Sequential )]
public class DGNElemCore
{
    public int offset;
    public int size;
    public int element_id;
    public int stype;          
    public int level;
    public int type;
    public int complex;
    public int deleted;
    public int graphic_group;
    public int properties;
    public int color;
    public int weight;
    public int style;
    public int attr_bytes;       
    public IntPtr attr_data;  
    public int raw_bytes;
    public IntPtr raw_data;                 

}

[DllImport("DgnLib.dll", EntryPoint = "DGNOpen")]           
public static extern IntPtr  DGNOpen(string fileName, int bUpdate)

Do you know how to fix this error ?

Solution

Add this along with dll import.

, CallingConvention = CallingConvention.Cdecl)]

As taken from here.

Platform invoke

To improve performance in interoperability with unmanaged code, incorrect calling conventions in a platform invoke now cause the application to fail. In previous versions, the marshaling layer resolved these errors up the stack.

Debugging your applications in Microsoft Visual Studio 2010 will alert you to these errors so you can correct them. If you have binaries that cannot be updated, you can include the element in your application's configuration file to enable calling errors to be resolved up the stack as in earlier versions. However, this may affect the performance of your application.