I'm trying to build generic function that get from user string and try to parse it to Enum valuse like this:
private Enum getEnumStringEnumType(Type i_EnumType) { string userInputString = string.Empty; Enum resultInputType; bool enumParseResult = false; while (!enumParseResult) { userInputString = System.Console.ReadLine(); enumParseResult = Enum.TryParse(userInputString, true, out resultInputType); } }
But i get:
The type 'System.Enum' must be a non-nullable value type in order to use it as parameter 'TEnum' in the generic type or method 'System.Enum.TryParse<TEnum>(string, bool, out TEnum) .
The Error means that i need to decalare a specific Enum for resultInputType? How can I fix this ? Thanks.
TryParse(Type, String, Object)Converts the string representation of the name or numeric value of one or more enumerated constants to an equivalent enumerated object.
TEnum is the Generic type of enumeration. You can pass any of your enumeration to that method. The second method is a non-generic one, where you would use a typeof keyword to identify the enums and return the enum names as a string collection.
The TryParse
method has the following signature:
TryParse<TEnum>(string value, bool ignoreCase, out TEnum result) where TEnum : struct
It has a generic type parameter TEnum
that must be a struct and that is used to determine the type of enumeration being parsed. When you don't provide it explicitly (as you did), it will take the type of whatever you provide as the result
argument, which in your case is of type Enum
(and not the type of the enumeration itself).
Note that Enum
is a class (despite it inheriting from ValueType
) and therefore it does not satisfy the requirement that TEnum
is a struct.
You can solve this by removing the Type
parameter and giving the method a generic type parameter with the same constraints (i.e. struct
) as the generic type parameter on the TryParse
function.
So try this, where I've named the generic type parameter TEnum
:
private static TEnum GetEnumStringEnumType<TEnum>() where TEnum : struct { string userInputString = string.Empty; TEnum resultInputType = default(TEnum); bool enumParseResult = false; while (!enumParseResult) { userInputString = System.Console.ReadLine(); enumParseResult = Enum.TryParse(userInputString, true, out resultInputType); } return resultInputType; }
To call the method, use:
GetEnumStringEnumType<MyEnum>();
You should make a generic method:
private T getEnumStringEnumType<T>() where T : struct, IConvertible { string userInputString = string.Empty; T resultInputType = default(T); bool enumParseResult = false; while (!enumParseResult) { userInputString = System.Console.ReadLine(); enumParseResult = Enum.TryParse<T>(userInputString, out resultInputType); } return resultInputType; }
usage:
public enum myEnum { val1, val2 } myEnum enumValue = getEnumStringEnumType<myEnum>();
If you love us? You can donate to us via Paypal or buy me a coffee so we can maintain and grow! Thank you!
Donate Us With