将VB.NET转换为C＃时出错

Question

Im trying convert at vb.net console file into C#, but i got 3 errors when i tried to run the console application, here are the errors.

Error   2   Single-line comment or end-of-line expected


private static MySettings defaultInstance = (MySettings)global::System.Configuration.ApplicationSettingsBase.Synchronized(new MySettings());
    #region "My.Settings Auto-Save Functionality"
    #if _MyType = "WindowsForms"    

Error   3   Single-line comment or end-of-line expected

        get {
            #if _MyType = "WindowsForms"
            if (!addedHandler) {
                lock (addedHandlerLockObject) {
                    if (!addedHandler) {
                        My.Application.Shutdown += AutoSaveSettings;
                        addedHandler = true;
                    }
                }
            }
            #endif
            return defaultInstance;


thanx

Answer 1

That's a build error, not a run-time error. In c#, the #if directive is much more limited than in other languages. From the language reference :

When the C# compiler encounters an #if directive, followed eventually by an #endif directive, it will compile the code between the directives only if the specified symbol is defined. Unlike C and C++, you cannot assign a numeric value to a symbol; the #if statement in C# is Boolean and only tests whether the symbol has been defined or not.

And note also the limitations of #define. Again from the reference :

You use #define to define a symbol. When you use the symbol as the expression that's passed to the #if directive, the expression will evaluate to true, as the following example shows:

#define DEBUG

The #define directive cannot be used to declare constant values as is typically done in C and C++. Constants in C# are best defined as static members of a class or struct. If you have several such constants, consider creating a separate "Constants" class to hold them.

So you need to do something like

#define WindowsForms
#if (!WindowsForms)
#define WPF
#endif

at the beginning of your file(s) rather than having a single preprocessor symbol with many possible values. For project-wide preprocessor symbols, use a /define option when compiling the project.

More here .