Indicates whether unmanaged methods that have HRESULT or retval return values are directly translated or whether HRESULT or retval return values are automatically converted to exceptions.
Syntax
Remarks
Set the DllImportAttribute.PreserveSig field to true to directly translate unmanaged signatures with HRESULT or retval values; set it to false to automatically convert HRESULT or retval values to exceptions. By default, the DllImportAttribute.PreserveSig field is true.
When true, the resulting method signature returns an integer value that contains the HRESULT value. In this case, you must manually inspect the return value and respond accordingly in your application.
When you set the DllImportAttribute.PreserveSig field to false, the resulting method signature contains a void return type instead of an integer (HRESULT) return type. When the unmanaged method produces an HRESULT, the runtime automatically ignores a return value of S_OK (or 0) and does not throw an exception. For HRESULTs other than S_OK, the runtime automatically throws an exception that corresponds to the HRESULT. Note that the System.Runtime.InteropServices.DllImportAttribute attribute only performs this conversion to methods that return an HRESULT.
You might decide to change the default error reporting behavior from HRESULTs to exceptions in cases where exceptions better fit the error reporting structure of your application.
This field is similar to the System.Runtime.InteropServices.PreserveSigAttribute; however, in contrast to the DllImportAttribute.PreserveSig field, the default value for the attribute is false.
In some cases, Visual Basic developers use the System.Runtime.InteropServices.DllImportAttribute, instead of using the Declare statement, to define a DLL function in managed code. Setting the DllImportAttribute.PreserveSig field is one of those cases.
Requirements
Assembly: mscorlib (in mscorlib.dll)
Assembly Versions: 1.0.5000.0, 2.0.0.0, 4.0.0.0