Reinterpret cast in C# , how?

Question

I have defined such a function:

public static void WriteResponse(ref HttpContext ctx, object sender, Type typeName)
{
    var model = sender as typeName; // it's an error-line, becase of `as typeName`
    var jsonObject = new JavaScriptSerializer().Serialize(model);
    ctx.Response.AddHeader("Access-Control-Allow-Origin", "*");
    ctx.Response.ContentType = "Content-type: application/json";
    ctx.Response.ContentEncoding = Encoding.UTF8;
    ctx.Response.Write(jsonObject);
}

As you can see, it wouldn't even compile, becase of the line:

var model = sender as typeName;

I'm calling this function from that one:

internal void GetShortInfo(ref HttpContext ctx, ref Shapefile shapefile)
{
    var model = new Models.SfShortInfo()
    {
        Count = shapefile.Count,
        Type = shapefile.Type.ToString()
    };

    ShapefileService.WriteResponse(ref ctx, (object)model, model.GetType());
}

And such a call:

ShapefileService.WriteResponse(ref ctx, (object)model, model.GetType());

I want to add to any function from self-designed API Web-service.

I think, that you've got an idea, what I'm trying TO DO.

I want to define one function, that could accept calls from various number of other functions by boxing the model instance to System.Object and unboxing it for the JSON-response.

It's similar to reinterpret_cast<> function in C++. I think, that I could done it in C# with the Generics, but I don't know very well that part of C#, so I'm advicing your help.

Thanks!

Answer 1

You don't need cast at all. The JavaScriptSerializer.Serialize method has this prototype:

public string Serialize(Object obj)

This means that your "unboxed" model will be boxed again and than you don't have to do this. Internally the function use Reflection and is able to read all Model metadata even it is passed to the method as object.

Using ref for HttpContext is not necessary and it is little bit dangerous because HttpContext is reference type and you can change reference in the called method. I have never seen good reason for pass reference type with ref keyword. It is useful mainly with value types.

Your solution can looks like:

public static void WriteResponse(HttpContext ctx, object model)
{
    string jsonObject = new JavaScriptSerializer().Serialize(model);
    ctx.Response.AddHeader("Access-Control-Allow-Origin", "*");
    ctx.Response.ContentType = "Content-type: application/json";
    ctx.Response.ContentEncoding = Encoding.UTF8;
    ctx.Response.Write(jsonObject);
}

Second point is that you don't have to cast model to object and you can pass model directly:

ShapefileService.WriteResponse(ctx, model);

If you really need strong type in the WriteResponse method, than you can use generic method:

public static void WriteResponse<T>(HttpContext ctx, T model)
{
    string jsonObject = new JavaScriptSerializer().Serialize(model);
    ctx.Response.AddHeader("Access-Control-Allow-Origin", "*");
    ctx.Response.ContentType = "Content-type: application/json";
    ctx.Response.ContentEncoding = Encoding.UTF8;
    ctx.Response.Write(jsonObject);
}

ShapefileService.WriteResponse<Models.SfShortInfo>(ctx, model);