Converto a String Into a T type C#

Question

I would like to create a function that has as input a string and return the converted string according to the T type.

I tried with

static T convertStringTemplate<T>(string myString)
        {
            return T.Parse(myString);
        }

However it does not work. Do you have any idea?

T can be any numeric type ( int, float, double,...) – Jun 10 '17 at 10:46 — , Jun 10 '17 at 10:46

score 1 · Answer 1 · answered Jun 10 '17 at 10:51

1

Generics don't work like that. Generics have to be instantiable for any T that matches the constraints (no limits in your case). convertStringTemplate<object> is a simple example that would pretty obviously not work.

You write in a comment:

T can be any numeric type ( int, float, double,...)

If it only has to work for numeric types, then it's much simpler. Just call Convert.ChangeType.

answered Jun 10 '17 at 10:51

I tried with `return Convert.ChangeType(myString, typeof(T));` however typeof does not recognize T – Jun 10 '17 at 11:00
@GVa Either you're misreading the error message (`Convert.ChangeType` returns `object`, which you can then cast to `T`, but if this is the problem, it's not about `typeof`), or you've not put it in a generic method with a generic type parameter named `T`. – Jun 10 '17 at 11:03

Federico Dipuma · Answer 2 · 2017-06-10T11:09:52.083

0

An easy way is to use the IConvertible interface:

static T ConvertStringTemplate<T>(string myString, IFormatProvider formatProvider = null)
{
    formatProvider = formatProvider ?? System.Globalization.CultureInfo.CurrentCulture;
    return (T)((IConvertible)myString).ToType(typeof(T), formatProvider);
}

If you want to restrict T to a numeric type, the closest constraint you may use is the following one (from this answer ):

static T ConvertStringTemplate<T>(string myString, IFormatProvider formatProvider = null)
    where T :
        struct, 
        IComparable, 
        IComparable<T>, 
        IConvertible, 
        IEquatable<T>, 
        IFormattable
{
    formatProvider = formatProvider ?? System.Globalization.CultureInfo.CurrentCulture;
    return (T)((IConvertible)myString).ToType(typeof(T), formatProvider);
}

Usage:

var x = ConvertStringTemplate<int>("12"); // results in 12

[Edit]
As stated in comments, you probably wanted to use the current culture while converting the string, so I added an IFormatProvider custom parameter to the method.

edited Jun 10 '17 at 11:09

answered Jun 10 '17 at 10:51

Federico Dipuma

17,655
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Heh, the `IConvertible` interface is exactly what `Convert.ChangeType` (which I suggested in my answer) would end up using anyway. You may want to avoid `InvariantCulture`. The OP attempted to call `T.Parse`, which if it worked would perform a culture-sensitive parse. – Jun 10 '17 at 10:52
@hvd Didn't know `Convert.ChangeType` used the `IConvertible` interface internally. Thanks for the clarification. – Federico Dipuma Jun 10 '17 at 10:57
This will blow up at runtime. – Kenneth K. Jun 10 '17 at 12:08
@KennethK. What should blow up? [DotNetFiddle here](https://dotnetfiddle.net/ugMd26) – Federico Dipuma Jun 10 '17 at 12:12

score -1 · Answer 3 · answered Jun 11 '17 at 12:44

-1

Creating an instance of a type whose name is specified, using the named assembly and default constructor, can be done with Activator.CreateInstance Method (String, String)

answered Jun 11 '17 at 12:44

Emiel Koning

4,039
1
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18

Converto a String Into a T type C#

3 Answers3