CODEWITHSUNDEEP
c#generics
Sachin Kainth
Sachin Kainth

Reputation: 46740

Returning one of many types from a string

I have a generic method.

private T Blah<T>()

In this method I have a string that I want to return, but the problem is that T may not be a string. The values T can be are string, int, DateTime, DateTime? and decimal?.

What do I do to this string so that I can return it and support all these types?

Upvotes: 0

Views: 82

Answers (3)

Ken Kin
Ken Kin

Reputation: 4693

I made Blah<T> public for test, modify it as your requirement.

  • Code 

    partial class SomeClass {
    public T Blah<T>() {
        var t="2013 03 30";

        return (T)(typeof(String).Equals(typeof(T))?t as object:(
            from args in new[] { new object[] { t, default(T) } }
            let type=Nullable.GetUnderlyingType(typeof(T))??typeof(T)
            let types=new[] { typeof(String), type.MakeByRefType() }
            let bindingAttr=BindingFlags.Public|BindingFlags.Static
            let tryParse=type.GetMethod("TryParse", bindingAttr, default(Binder), types, null)
            let b=typeof(DateTime)!=type
            let dummy=b?args[0]=((String)args[0]).Split('\x20').Aggregate(String.Concat):""
            let success=null!=tryParse?tryParse.Invoke(typeof(T), args):false
            select args.Last()).Last());
    }
}


    partial class TestClass {
    public static void TestMethod() {
        var x=new SomeClass();

        Console.WriteLine("x.Blah<String>() = {0}", x.Blah<String>());
        Console.WriteLine("x.Blah<int>() = {0}", x.Blah<int>());
        Console.WriteLine("x.Blah<DateTime>() = {0}", x.Blah<DateTime>());
        Console.WriteLine("x.Blah<DateTime?>() = {0}", x.Blah<DateTime?>());
        Console.WriteLine("x.Blah<decimal?>() = {0}", x.Blah<decimal?>());
    }
}

  • Output 

    x.Blah<String>() = 2013 03 30
x.Blah<int>() = 20130330
x.Blah<DateTime>() = 2013/3/30 0:00:00
x.Blah<DateTime?>() = 2013/3/30 0:00:00
x.Blah<decimal?>() = 20130330

The special thing is that I removed the spaces if destination type is not DateTime or DateTime?.

You can even try with x.Blah<long>() which is not in your requirement, and any other types. Let me know if you found any type can cause an exception.

Upvotes: 1

Hossein Narimani Rad
Hossein Narimani Rad

Reputation: 32481

This may help:

private T Blah<T>(Func<string, T> map)
{   
    //Your codes here

    return map(yourString); //yourString: the string which you are going to convert
}

Here you call it:

//For int
Blah(input => int.Parse(input));

//For DateTime
Blah(input => DateTime.Parse(input));

Upvotes: 1

Rob G
Rob G

Reputation: 3526

  private T Blah<T> () where T : IConvertible
  {            
     if (!String.IsNullOrEmpty(source))
          return (T)Convert.ChangeType(source, typeof(T));
     return default(T);
  }

Should work for all those types.

Upvotes: 4

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