Visual Studio 2019 recommended converting a switch statement I had written to a switch expression (both included below for context).
For a simple example such as this, is there any technical or performance advantage to writing it as an expression? Do the two versions compile differently for example?
Statement
switch(reason)
{
case Reasons.Case1: return "string1";
case Reasons.Case2: return "string2";
default: throw new ArgumentException("Invalid argument");
}
Expression
return reason switch {
Reasons.Case1 => "string1",
Reasons.Case2 => "string2",
_ => throw new ArgumentException("Invalid argument")
};
The result of a switch expression is the value of the expression of the first switch expression arm whose pattern matches the input expression and whose case guard, if present, evaluates to true . The switch expression arms are evaluated in text order.
The expression used in a switch statement must have an integral or enumerated type, or be of a class type in which the class has a single conversion function to an integral or enumerated type. You can have any number of case statements within a switch. Each case is followed by the value to be compared to and a colon.
Java SE 12 introduced switch expressions, which (like all expressions) evaluate to a single value, and can be used in statements.
if-else better for boolean values: If-else conditional branches are great for variable conditions that result into a boolean, whereas switch statements are great for fixed data values.
In the example you give there's not a lot in it really. However, switch expressions are useful for declaring and initializing variables in one step. For example:
var description = reason switch
{
Reasons.Case1 => "string1",
Reasons.Case2 => "string2",
_ => throw new ArgumentException("Invalid argument")
};
Here we can declare and initialize description
immediately. If we used a switch statement we'd have to say something like this:
string description = null;
switch(reason)
{
case Reasons.Case1: description = "string1";
break;
case Reasons.Case2: description = "string2";
break;
default: throw new ArgumentException("Invalid argument");
}
One downside of switch expressions at the moment (in VS2019 at least) is that you can't set a breakpoint on an individual condition, only the whole expression. However, with switch statements you can set a breakpoint on an individual case statement.
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