Compiler Error CS0406 

Error Message

The class type constraint 'constraint' must come before any other constraints

When a generic type or method has a class type constraint, that constraint must be listed first. To avoid this error, move the class type constraint to the beginning of the constraint list.

Example

The following sample generates CS0406.

// CS0406.cs
// compile with: /target:library
interface I {}
class C {}
class D<T> where T : I, C {}   // CS0406
class D2<T> where T : C, I {}   // OK

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