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Compiler Error C3392

  • Artikkeli

'type_arg' : invalid type argument for generic parameter 'param' of generic 'generic_type', must have a public parameterless constructor

A generic type was instantiated incorrectly. Check the type definition. For more information, see Generics.

Example

The following sample uses C# to create a component that contains a generic type that has certain constraints that are not supported when authoring generic types in C++/CLI. For more information, see Constraints on Type Parameters.

// C3392.cs
// Compile by using: csc /target:library C3392.cs
// a C# program
public class GR<C, V, N>
where C : class
where V : struct
where N : new() {}

When the C3392.dll component is available, the following sample generates C3392.

// C3392_b.cpp
// Compile by using: cl /clr C3392_b.cpp
#using <C3392.dll>

ref class R { R(int) {} };
ref class N { N() {} };

value class V {};

ref class N2 { public: N2() {} };
ref class R2 { public: R2() {} };

int main () {
   GR<R^, V, N^>^ gr1;   // C3392
   GR<R^, V, N2^>^ gr1a; // OK

   GR<R^, N^, N^>^ gr3;  // C3392
   GR<R^, V, N2^>^ gr3a; // OK

   GR<R^, V, R^>^ gr4;   // C3392
   GR<R^, V, R2^>^ gr4a; // OK
}