Cannot define T in C# [duplicate]

Question

Any clue how to define T in this code?

 public static T ToEnum<T>(this string value, T defaultValue) { if (string.IsNullOrEmpty(value)) { return defaultValue; } T result; return Enum.TryParse<T>(value, true, out result) ? result : defaultValue; }

Severity Code Description Project File Line Error CS0453 The type 'T' must be a non-nullable value type in order to use it as parameter 'TEnum' in the generic type or method 'Enum.TryParse(string, bool, out TEnum)'

@PetSerAl Please write out the whole code like an answer. Thank you! — NoWar
– NoWar, Commented Jan 15, 2016 at 18:40
Please read How to Ask. If you can define "this", you can search for it. Do you want a "generic type constraint for an enum"? — CodeCaster
– CodeCaster, Commented Jan 15, 2016 at 18:43

Felipe Oriani · Accepted Answer · 2016-01-15 19:14:50Z

4

Try using a constraint to have a value type which is a struct, for sample:

public static T ToEnum<T>(this string value, T defaultValue) where T : struct { if (string.IsNullOrEmpty(value)) { return defaultValue; } T result; return Enum.TryParse<T>(value, true, out result) ? result : defaultValue; }

I haven't tested it.

edited Jan 15, 2016 at 19:14

answered Jan 15, 2016 at 18:41

Felipe Oriani

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5 Comments

Camilo Terevinto Over a year ago

Beat me by a second!

NoWar Over a year ago

It gives the error

Severity	Code	Description	Project	File	Line Error	CS0451	The 'new()' constraint cannot be used with the 'struct' constraint

Felipe Oriani Over a year ago

Try using the ´Enum` as a constraint!

Camilo Terevinto Over a year ago

Just remove , new() OP, an enum cannot be "new"

Rob Over a year ago

where T : Enum is not a valid template constraint in C#.

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