How to get enum value by string or int

How can I get the enum value if I have the enum string or enum int value. eg: If i have an enum as follows:

public enum TestEnum
{
    Value1 = 1,
    Value2 = 2,
    Value3 = 3
}

and in some string variable I have the value "value1" as follows:

string str = "Value1"

or in some int variable I have the value 2 like

int a = 2;

how can I get the instance of enum ? I want a generic method where I can provide the enum and my input string or int value to get the enum instance.

No, you don't want a generic method. This is much easier:

MyEnum myEnum = (MyEnum)myInt;

MyEnum myEnum = (MyEnum)Enum.Parse(typeof(MyEnum), myString);

I think it will also be faster.

There are numerous ways to do this, but if you want a simple example, this will do. It just needs to be enhanced with necessary defensive coding to check for type safety and invalid parsing, etc.

    /// <summary>
    /// Extension method to return an enum value of type T for the given string.
    /// </summary>
    /// <typeparam name="T"></typeparam>
    /// <param name="value"></param>
    /// <returns></returns>
    public static T ToEnum<T>(this string value)
    {
        return (T) Enum.Parse(typeof(T), value, true);
    }

    /// <summary>
    /// Extension method to return an enum value of type T for the given int.
    /// </summary>
    /// <typeparam name="T"></typeparam>
    /// <param name="value"></param>
    /// <returns></returns>
    public static T ToEnum<T>(this int value)
    {
        var name = Enum.GetName(typeof(T), value);
        return name.ToEnum<T>();
    }

Could be much simpler if you use TryParse or Parse and ToObject methods.

public static class EnumHelper
{
    public static  T GetEnumValue<T>(string str) where T : struct, IConvertible
    {
        Type enumType = typeof(T);
        if (!enumType.IsEnum)
        {
            throw new Exception("T must be an Enumeration type.");
        }
        return Enum.TryParse(str, true, out T val) ? val : default;
    }

    public static T GetEnumValue<T>(int intValue) where T : struct, IConvertible
    {
        Type enumType = typeof(T);
        if (!enumType.IsEnum)
        {
            throw new Exception("T must be an Enumeration type.");
        }
        
        return (T)Enum.ToObject(enumType, intValue);
    }
}

As noted by @chrfin in comments, you can make it an extension method very easily just by adding this before the parameter type which can be handy.

How to get enum value by string or int

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