Client code can only access these return codes by handling the exception. For example, in C#: 

try
{
    // Some SOLIDWORKS PDM Professional call that results in an exception
}
catch (System.Runtime.InteropServices.ComException comEx)
{
    switch (comEx.ErrorCode)
    {
        case S_EDM_xxx:
            // respond to xxx
            break;
        case S_EDM_yyy:
            // respond to yyy
            break;
        default:
            // Unexpected or cannot be handled silently
            // Use IEdmVault5::GetErrorString or IEdmVault11::GetErrorMessage to prepare a message for the user or log
            break;
    }
}

HRESULT return codes are supported by the SOLIDWORKS PDM Professional API. You can pass the HRESULT code to the method IEdmVault11::GetErrorMessage to get information about the code. 

Client code can only access these success codes by handling the exception; i.e., via System.Runtime.InteropServices.ComException.  

NOTES:

• Methods called from Visual Basic do not return the HRESULT code directly. Instead, the return codes are returned as an argument declared with the [retval] directive, if one exists. Visual Basic users can view the error codes returned by methods by implementing an error handler and checking the Number property of the Err object. The property is the HRESULT return code from the failing method.
• The values shown in this topic are written in C++ style hexadecimal notation. In VB.NET, the value 0x80040200 is written as &H80040200.