If it is a C # DLL, you can use ildasm (Program Files \ Microsoft SDKs \ Windows \ v6.0A \ bin \ ildasm.exe) to find out this information.
1) Drag DLL to ILDASM
2) Dbl-Click on MANIFEST
3) Look for:
//.custom instance void [mscorlib] System.Diagnostics.DebuggableAttribute ::. ctor (valuetype [mscorlib] System.Diagnostics.DebuggableAttribute / DebuggingModes) = (01 nn nn nn nn nn nn nn)
4) DEBUG DLL (01 00 07 01 00 00 00 00)
(01 00 02 00 00 00 00 00) (01 00 03 00 00 00 00)
, ! BTW , , .