safe_cast
safe_cast allows you to change the type of an expression and generate verifiable MSIL code.
[cli]::safe_cast<type-id>(expression)
Parameters
- type-id
A handle to a reference or value type, a value type, or a tracking reference to a reference or value type.
- source
An expression that evaluates to a handle to a reference or value type, a value type, or a tracking reference to a reference or value type.
Remarks
The expression safe_cast<type-id>(expression) converts the operand expression to an object of type type-id.
The compiler will accept a static_cast in most places that it will accept a safe_cast. However, safe_cast is guaranteed to produce verifiable MSIL, where as a static_cast could produce unverifiable MSIL. See Pure and Verifiable Code and PEVerify Tool (Peverify.exe) for more information on verifiable code.
Like static_cast, safe_cast invokes user-defined conversions.
safe_cast is a keyword defined inside the cli namespace, which is a compiler-defined namespace. For more information, see cli Namespace.
For more information about casts, see Casting Operators.
safe_cast does not apply a const_cast (cast away const).
safe_cast is in the cli namespace. See cli Namespace for more information.
For more information on safe_cast, see:
Example
One example of where the compiler will not accept a static_cast but will accept a safe_cast is for casts between unrelated interface types. With safe_cast, the compiler will not issue a conversion error and will perform a check at runtime to see if the cast is possible
// safe_cast.cpp
// compile with: /clr
using namespace System;
interface class I1 {};
interface class I2 {};
interface class I3 {};
ref class X : public I1, public I2 {};
int main() {
I1^ i1 = gcnew X;
I2^ i2 = safe_cast<I2^>(i1); // OK, I1 and I2 have common type: X
// I2^ i3 = static_cast<I2^>(i1); C2440 use safe_cast instead
try {
I3^ i4 = safe_cast<I3^>(i1); // fail at runtime, no common type
}
catch(InvalidCastException^) {
Console::WriteLine("Caught expected exception");
}
}
Output
Caught expected exception