How Can I Work Around the Lack of Enum Generic Constraints in C#?

Solving the problem of missing enumeration generic constraints in C#

C# lacks enumeration generic constraints, which creates limitations when creating extension methods for enumerations. However, there are some workarounds.

A recommended approach is to use the UnconstrainedMelody library. The library allows specifying "pseudo" constraints such as where T : struct, IEnumConstraint, which UnconstrainedMelody converts to where T : struct, System.Enum during the post-build process.

Another workaround is to implement the required functionality manually. For example, consider the following IsSet method:

<code class="language-csharp">public static bool IsSet<T>(this T input, T matchTo)
    where T : struct // 不是枚举约束
{
    return (input & matchTo) != 0;
}</code>

When this method is called with multiple flags, it may not provide the desired behavior because it only checks for the presence of a single flag.

To solve this problem, you can define an additional method:

<code class="language-csharp">public static bool HasFlags<T>(this T input, params T[] matchTo)
    where T : struct // 不是枚举约束
{
    foreach (var flag in matchTo)
    {
        if ((input & flag) == 0)
            return false;
    }

    return true;
}</code>

This method iterates over the specified flags and returns true only if all flags are set.

Naming Convention

The appropriate naming convention for these methods depends on preference. Possible options include:

• Includes
• Contains
• HasFlag (or HasFlags)
• IsSet

The final decision may vary depending on the specific context and usage of the method.

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