How to cast an object of type Object to a object of type T?

Question

I've written a method that executes JavaScript and return value. The returned value could be literately anything. Now I'd like at least to cut the number of repeated code by writing an generic overload.

something like:

public T ExecuteJavascriptWithReturnValue<T>(string js)
{
 object obj = ExecuteJavascriptWithReturnValue(js); --the original method returns an object
 if (typeof(T) == typeof(int) || typeof(T) == typeof(double) ||typeof(T) == typeof(string))
      return (T)(obj);
}
else
{
   throw new Exception("For objects other than int, float, double, or string, please use the non generic version.");
}

I'm getting the the following error: specified cast is not valid. The only time this code works is when the object returned is of type string.

Thanks for helping.

EDIT

public object ExecuteJavascriptWithReturnValue(string js)
{
   IJavaScriptExecutor jse = driver as IJavaScriptExecutor;
   object result = jse.ExecuteScript(js);
   return result;
}

This method can return litteraly anything, for instance, a collections, a string, a number, etc. Here's the metadata:

...object ExecuteScript(string script, params object[] args);

and a script could be something like:

string js = "return $('#calculateValueStep > span.k-widget.k-numerictextbox > span >"
          + " input.k-formatted-value.k-input').val();";

I use this method often. So, I want a generic method for those time I'm expecting an object of type, such as int, double, and son forth.

Did you see [this](http://stackoverflow.com/questions/899629/cast-object-to-t)? — Yacoub Massad, Oct 21 '15 at 21:40
Well if it's giving you that error, presumably the object isn't of the type you're trying to cast it to. I suggest you log `obj.GetType()` to find out what it really is... (It doesn't help that we have no idea how your `ExecuteJavascriptWithReturnValue` method works. It's entirely possible that it models all numbers as `double` values...) — Jon Skeet, Oct 21 '15 at 21:42
is this a parse or cast problem? if you try (int) Object and it is integer it should work. It suggests you type expectations are wrong. You say it works for string... sounds more like a parsing scenario — phil soady, Oct 21 '15 at 22:08

Festyk · Accepted Answer · 2015-10-22T15:12:04.227

2

Maybe try this:

 return (T)Convert.ChangeType(obj, typeof(T));

edited Oct 22 '15 at 15:12

answered Oct 21 '15 at 21:50

Festyk

316
1
6

2

dont forget to cast it to T – M.kazem Akhgary Oct 21 '15 at 21:51
Adding `(T)` in the front, as @M.kazemAkhgary suggested, works. – Richard77 Oct 22 '15 at 14:56
Ok, I edited my answer to be completely working solution. – Festyk Oct 22 '15 at 15:12

How to cast an object of type Object to a object of type T?

EDIT

1 Answers1