CODEWITHSUNDEEP
c#dynamiccastingchangetype
Richard
Richard

Reputation: 455

Casting with types from a string

I am attempting to dynamically cast a variable to any type from a string in c#. Here is an example:

string str = "System.Int32";
Type t = System.Type.GetType(str);
string v = "100";
System.Int32 x = Convert.ChangeType(v,t);

The error that is displayed at design-time is:

Cannot implicitly convert type 'object' to 'int.' An explicit conversion exists (Are you missing a cast?)

What is the easiest way to accomplish this? I realize that the example above shows casting to an int32, but that is purely for the example. I do not know the type ahead of time. I apologize for not making that clear on my original question.

Upvotes: 0

Views: 393

Answers (3)

sa_ddam213
sa_ddam213

Reputation: 43636

You could make a hepler method to make it a bit easier

public T ConvertTo<T>(object obj) where T : IConvertible
{
    try
    {
        return (T)Convert.ChangeType(obj, typeof(T));
    }
    catch
    {  // handle as needed/required
    }
    return default(T);
}

Usage:

string v = "100";
int value = ConvertTo<int>(v);

Or Extension method:

public static class Extensions
{
    public static T ConvertTo<T>(this object obj) where T : IConvertible
    {
        try
        {
            return (T)Convert.ChangeType(obj, typeof(T));
        }
        catch
        {  // handle as needed/required
        }
        return default(T);
    }
}

Usage:

string v = "100";
int value = v.ConvertTo<int>();

Upvotes: 1

Dan
Dan

Reputation: 9847

If you know the type that you're trying to convert to, you should just cast it to that type:

int x = (int)Convert.ChangeType(v, t);

It might also be nice to have a generic method to perform the cast for you:

public static class ConvertHelper
{
    public static T ChangeType<T>(string value)
    {
      return (T)Convert.ChangeType(value, typeof(T));
    }
}

...

int x = ConvertHelper.ChangeType<int>(v);

Upvotes: 0

JaredPar
JaredPar

Reputation: 755457

The ChangeType function has a return type of Object. You need to explicitly cast to Int32

System.Int32 x = (System.Int32)Convert.ChangeType(v,t);

Couple of other minor points

  • It's more idiomatic to use the nameint instead of System.Int32
  • Instead of "System.Int32" use typeof(int).FullName

Upvotes: 1

Related Questions