How should I convert a string to an enum in C#?

What's the best way to convert a string to an enumeration value in C#?

I have an HTML select tag containing the values of an enumeration. When the page is posted, I want to pick up the value (which will be in the form of a string) and convert it to the enumeration value.

In an ideal world, I could do something like this:

StatusEnum MyStatus = StatusEnum.Parse("Active");

but that isn't a valid code.

---

In .NET Core and .NET >4 there is a generic parse method:

Enum.TryParse("Active", out StatusEnum myStatus);

This also includes C#7's new inline out variables, so this does the try-parse, conversion to the explicit enum type and initialises+populates the myStatus variable.

If you have access to C#7 and the latest .NET this is the best way.

Original Answer

In .NET it's rather ugly (until 4 or above):

StatusEnum MyStatus = (StatusEnum) Enum.Parse(typeof(StatusEnum), "Active", true);

I tend to simplify this with:

public static T ParseEnum<T>(string value)
{
    return (T) Enum.Parse(typeof(T), value, true);
}

Then I can do:

StatusEnum MyStatus = EnumUtil.ParseEnum<StatusEnum>("Active");

One option suggested in the comments is to add an extension, which is simple enough:

public static T ToEnum<T>(this string value)
{
    return (T) Enum.Parse(typeof(T), value, true);
}

StatusEnum MyStatus = "Active".ToEnum<StatusEnum>();

Finally, you may want to have a default enum to use if the string cannot be parsed:

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;
}

Which makes this the call:

StatusEnum MyStatus = "Active".ToEnum(StatusEnum.None);

However, I would be careful adding an extension method like this to string as (without namespace control) it will appear on all instances of string whether they hold an enum or not (so 1234.ToString().ToEnum(StatusEnum.None) would be valid but nonsensical) . It's often be best to avoid cluttering Microsoft's core classes with extra methods that only apply in very specific contexts unless your entire development team has a very good understanding of what those extensions do.

---

Use Enum.TryParse<T>(String, T) (≥ .NET 4.0):

StatusEnum myStatus;
Enum.TryParse("Active", out myStatus);

It can be simplified even further with C# 7.0's parameter type inlining:

Enum.TryParse("Active", out StatusEnum myStatus);

---

Note that the performance of Enum.Parse() is awful, because it is implemented via reflection. (The same is true of Enum.ToString, which goes the other way.)

If you need to convert strings to Enums in performance-sensitive code, your best bet is to create a Dictionary<String,YourEnum> at startup and use that to do your conversions.

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