Dereference of a possibly null reference.

Theory method 'DataTest' on test class 'XunitTests' does not use parameter 'number'. Use the parameter, or remove the parameter and associated data. (https://xunit.net/xunit.analyzers/rules/xUnit1026)

Nullability of reference types in type of parameter 'value' doesn't match implemented member 'int IList.Add(object? value)' (possibly because of nullability attributes).

Nullability of reference types in type of parameter 'value' doesn't match implemented member 'bool IList.Contains(object? value)' (possibly because of nullability attributes).

Nullability of reference types in type of parameter 'value' doesn't match implemented member 'int IList.IndexOf(object? value)' (possibly because of nullability attributes).

Nullability of reference types in type of parameter 'value' doesn't match implemented member 'void IList.Insert(int index, object? value)' (possibly because of nullability attributes).

Nullability of reference types in type of parameter 'value' doesn't match implemented member 'void IList.Remove(object? value)' (possibly because of nullability attributes).

Nullability of reference types in type of parameter 'value' doesn't match implemented member 'void IList.this[int index].set' (possibly because of nullability attributes).

Possible null reference assignment.