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'TryCast' operands must be class-constrained type parameters, but '<typeparametername>' has no class constraint

The TryCast operator is used with a type parameter operand that is not guaranteed to be a reference type.

TryCast operates only on reference types, such as classes or interfaces. When you pass a type parameter as an argument to TryCast, you must constrain that type parameter to be a reference type. You can do this by including one or more of the following in the type parameter's constraint list:

  • One or more interface names (the type argument must implement all of them)

  • At most one class name (the type argument must inherit from it)

  • The New (Visual Basic) constraint (the type argument must expose a parameterless constructor that the creating code can access, and therefore it must be a class)

  • The Class (Visual Basic) constraint (the type argument must be a reference type)

Error ID: BC30793

To correct this error

  • If you need to pass this type parameter to TryCast, constrain it with one or more of the constraints in the preceding list.

  • If you cannot require the type parameter to accept only a reference type, you cannot use it with TryCast. You might be able to use the CType Function instead.

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