c# - Can using UnmanagedMemory.LPTStr instead of .ByValTStr result in memory corruption? Why? -

we have tree view in windows forms app shows files using appropriate file icon using following code. problem call geticon() appears corrupt memory start getting various program crashes can't catch debugger after call.
program work when change managedtype.lptstr managedtype.byvaltstr. true fix or masking problem?

this code appeared working in our last product release , can't see has changed. using .net 4.0. see issue in release mode.

[dllimport("shell32.dll")] private static extern int  shgetfileinfo(string pszpath, uint dwfileattributes, out shfileinfo psfi, uint cbfileinfo, shgfi uflags);   [structlayout(layoutkind.sequential)]         private struct shfileinfo         {             public shfileinfo(bool b)             {                 hicon=intptr.zero;                 iicon=0;                 dwattributes=0;                                 szdisplayname = "";                                 sztypename = "";             }              public intptr hicon;             public int iicon;             public uint dwattributes;                          [marshalas(unmanagedtype.lptstr, sizeconst = 260)]//works if .byvaltstr used instead                         public string szdisplayname;                         [marshalas(unmanagedtype.lptstr, sizeconst = 80)]//works if .byvaltstr used instead                         public string sztypename;         };   public static icon geticon(string strpath, bool bsmall)         {             shfileinfo info = new shfileinfo(true);             int cbfileinfo = marshal.sizeof(info);             shgfi flags;             if (bsmall)                 flags = shgfi.icon|shgfi.smallicon|shgfi.usefileattributes;             else                 flags = shgfi.icon|shgfi.largeicon|shgfi.usefileattributes;              shgetfileinfo(strpath, 256, out info,(uint)cbfileinfo, flags);             return icon.fromhandle(info.hicon);         } 

well, it's not proper lpstr in struct, can't try marshal 1 , expect work:

typedef struct _shfileinfo {   hicon hicon;   int   iicon;   dword dwattributes;   tchar szdisplayname[max_path];   tchar sztypename[80]; } shfileinfo; 

• lptstr use when you've allocated special block of memory hold string (usually in marshal.allochglobal or similar), you've copied on string unmanaged memory area.

• byvaltstr use when literally passing in actual string value, not reference area in memory.

the struct wants proper value, not pointer.