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How do I compare values of generic types?
I have reduced it to a minimal sample:
public class Foo<T> where T : IComparable { private T _minimumValue = default(T); public bool IsInRange(T value) { return (value >= _minimumValue); // <-- Error here } } The error is:
Operator '>=' cannot be applied to operands of type 'T' and 'T'.
What on earth!? T is already constrained to IComparable, and even when constraining it to value types (where T: struct), we still can't apply any of the operators <, >, <=, >=, == or !=. (I know that workarounds involving Equals() exist for == and !=, but it doesn't help for the relational operators).
So, two questions:
IComparable? Doesn't it somehow defeat the entire purpose of generic constraints?(I realize there are already a handful of questions related to this seemingly simple problem - but none of the threads gives an exhaustive or workable answer, so here.)
856
To enable two objects of a generic type parameter to be compared, they must implement the IComparable or IComparable<T>, and/or IEquatable<T> interfaces. Both versions of IComparable define the CompareTo() method and IEquatable<T> defines the Equals() method.
If you need to compare objects of type T for equality/inequality, you can use the IEquatable<T> interface.
Use the IsGenericType property to determine whether the type is generic, and use the IsGenericTypeDefinition property to determine whether the type is a generic type definition. Get an array that contains the generic type arguments, using the GetGenericArguments method.
IComparable doesn't overload the >= operator. You should use
value.CompareTo(_minimumValue) >= 0 If value can be null the current answer could fail. Use something like this instead:
Comparer<T>.Default.Compare(value, _minimumValue) >= 0 If you love us? You can donate to us via Paypal or buy me a coffee so we can maintain and grow! Thank you!
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