Want to validate a function and execute it

[Anindya Chatterjee]

I have a typical problem. It is like I want to execute some API calls based on the Platform, if one API is not supported by the current platform it will throw an exception. I want to implement it like this: [Platform(Platform.Win32NT)] [DllImport("somedll.dll")] public static extern int APIcall([In] int param1, float param2); public int CallTheAPI(int param1, float param2) { return APICall(parma1, param2); //If the current platform is not Win32NT it should throw an Error } How should I implement Platform attribute and accomplish the operation? Please give some idea.

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[Tuwing Sabado]

try this one. [Platform(Platform.Win32NT)] [DllImport("somedll.dll")] public static extern int APIcall([In] int param1, float param2); public int CallTheAPI(int param1, float param2) { if (!System.Environment.OSVersion.Platform.ToString().Equals("Win32NT")) { throw new ApplicationException("Your current platform is not a Win32NT operating system."); } return APICall(parma1, param2); //If the current platform is not Win32NT it should }

[Anindya Chatterjee]

Basically , this is ok for one or two api calls. But I am here handling with more than 300 calls. So instead of putting the if conditions everywhere , just using attribute over each api signature would be lot easier. That is why i am posting this question to get it in a easier way.

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[S Senthil Kumar]

I guess you're looking for a generic method dispatch mechanism that validates the platform before executing calls. How about something like this.

enum Platform
{
    XP,
    NT,
    Vista
}

class PlatformNameAttribute : Attribute
{
    public PlatformNameAttribute(Platform platForm)
    {
        this.Platform = platForm;
    }

    public Platform Platform { get; set; }
}

class Program
{
    \[PlatformName(Platform.NT)\]
    static void SomeAPICall()
    {
        Console.WriteLine("NT");
    }

    \[PlatformName(Platform.XP)\]
    static void SomeOtherAPICall(int x)
    {
        Console.WriteLine("XP");
    }

    static Platform GetCurrentPlatform() { return Platform.NT; }

    static void ExecuteAPICall(Delegate d, params object\[\] parameters)
    {
        var attributes = d.Method.GetCustomAttributes(typeof(PlatformNameAttribute), false);

        if (attributes != null && attributes.Count() > 0)
        {
            var platformAttribute = (PlatformNameAttribute)attributes\[0\];

            if (platformAttribute.Platform != GetCurrentPlatform())
            {
                throw new InvalidOperationException("Platform Type mismatch");
            }

            d.DynamicInvoke(parameters);
        }
    }

    static void Main(string\[\] args)
    {
        ExecuteAPICall(new Action(SomeAPICall));
        ExecuteAPICall(new Action<int>(SomeOtherAPICall), 2);
    }

You could do something more typesafe than DynamicInvoke, with Expression and lambdas, but that would require .NET 3.5, and I'm not sure you are running it.

Regards Senthil [MVP - Visual C#] _____________________________ My Home Page |My Blog | My Articles | My Flickr | WinMacro

[Anindya Chatterjee]

That's a cool solution and I already tried it. But the problem is when API calls uses parameters with ref / out keyword or it has a large number of parameters say 7 or something or have parameters with marshalas attributes you can't use either Action or Func. I am not sure in that case if this method dispatcher will work or not. For your information I am using .Net 3.5. Any kind of suggestion is highly required. Thanks.

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