In C#, covariance and contravariance enable implicit reference conversion for array types, delegate types, and generic type arguments.Covariance preserves assignment compatibility and contravariance reverses it.

In C#, variance is supported in the following scenarios:

1. Covariance in arrays (since C# 1.0)

2. Covariance and contravariance in delegates, also known as “method group                 variance” (since C# 2.0)

3. Variance for generic type parameters in interfaces and delegates (since C# 4.0)

Arrays are covariant since C# 1.0. You can always do the following:

object[] obj = new String[10];

What is array covariance?

Arrays are covariant since C# 1.0. You can always do the following:

object[] obj = new String[10];

Covariance in arrays is considered “not safe,” because you can also do this:

obj[0] = 5;

This code compiles, but it throws an exception at run time because obj is in fact an array of strings and cannot contain integers.