Alternative to VB.NET's Type Conversion functi

问题:

Is there any alternative to VB's CBool keyword in C#?

What about all the other functions?

CBool will turn to a Boolean any valid boolean: 0, "False", null etc.

回答1:

The trick is that the Cxx "functions" in VB.NET aren't actually functions. In fact, they're more like operators that the compiler translates to what it determines is the "best-match" type conversion.

Paul Vick used to have a great article about this on his blog, but all those pages seem to have been taken down now. MSDN (which is mostly accurate here) says:

These functions are compiled inline, meaning the conversion code is part of the code that evaluates the expression. Sometimes there is no call to a procedure to accomplish the conversion, which improves performance. Each function coerces an expression to a specific data type.

The options it has available to do so include a direct cast (such as: (bool)var), an attempt to cast (using the as operator), calling one of the methods defined in the System.Convert class, calling the applicable Type.Parse method, and maybe some other strategies.

There's no direct equivalent of this in C#: you have to do the compiler's thinking instead.

In this case, you'll almost certainly want to use the appropriate overload of the Convert.ToBoolean method because that particular method will have the necessary logic to convert the value into a bool. A direct cast won't work here.

回答2:

Take a look at the System.Convert class.

回答3:

If you expect to be converting from one of the string values: "True", "true", "False", or "false", you should use Boolean.Parse. Instead of trying to be "smart" about it, Parse will "fail fast" if it doesn't get what it expects. By using a "smart" conversion when you don't really need it, you may mask errors at their source then have to track them down when they appear later in the code, which is usually more difficult.