facing issue with Projectwise aaApi_GetDocumentStringProperty(DOC_PROP_FILENAME,i) using C#

Question

Hi 
 I am using Projectwise APIs in C# using DLLImports, all my other APIs work without any failure. But when I tried to aaApi_GetDocumentStringProperty(DOC_PROP_FILENAME,i) API my program terminated without giving any error. Can anyone help me to figure out this. 
 
 My code, 
 [ DllImport ( @"C:\Program Files (x86)\Bentley\ProjectWise\Bin\dmscli.dll" , CharSet = CharSet .Unicode, SetLastError = true )] 
 public static extern string aaApi_GetDocumentStringProperty( int lPropertyId, int lIndex); 
 function() 
 { 
 int Count = PWAPIs.aaApi_SelectDocumentsByProjectId(project_no); 
 for (i = 0; i < Count; i++) 
 { 
 string fileName = PWAPIs.aaApi_GetDocumentStringProperty(DOC_PROP_FILENAME, i); 
 ... 
 .. 
 } 
 }

Regards, 
 Atul Dusane

Bruce Shearer · Accepted Answer

The API call returns a pointer, so you'll need something like this: 
 
 [DllImport("dmscli.dll", CharSet = CharSet.Unicode)] 
 private static extern IntPtr aaApi_GetDocumentStringProperty(DocumentProperty PropertyId, int Index); 
 
Then marshal it to a string with something like this: 
 
 string fileName = Marshal.PtrToStringUni(aaApi_GetDocumentStringProperty(PropertyId, Index));

Dean Lyon · Answer

Try this approach. I had to do this sometimes to get things to work in a x64 build.

[DllImport(@"C:\Program Files (x86)\Bentley\ProjectWise\Bin\dmscli.dll", CharSet = CharSet.Unicode] 
 public static extern IntPtr aaApi_GetDocumentStringProperty(int lPropertyId,int lIndex); 
 
 ..... Then in the code ..... 
 string Filename = ""; 
 IntPtr hFilename = PWAPIs.aaApi_GetDocumentStringProperty(DOC_PROP_FILENAME, i); 
 if(hFilename != IntPtr.zero) //check for null 
 { Filename = Marshal .PtrToStringUni(hFilename);}

Atul · Answer

Thanks