PrepareConstrainedRegions方法

private static void Demo1() {
   try {
      Console.WriteLine("In try");
   }
   finally {
      // Type1!ˉs static constructor is implicitly called in her
      Type1.M();
   }
}
 
private sealed class Type1 {
   static Type1() {
      // if this throws an exception, M won!ˉt get calle
      Console.WriteLine("Type1's static ctor called");
   }
 
   public static void M() { }
}

When I run the code above, I get the following output:
In try
Type1's static ctor called

 

private static void Demo2() {
   // Force the code in the finally to be eagerly prepared
   RuntimeHelpers.PrepareConstrainedRegions();  // System.Runtime.CompilerServices namespace
   try {
      Console.WriteLine("In try");
   }
   finally {
      // Type2!ˉs static constructor is implicitly called in her
      Type2.M();
   }
}
 
public class Type2 {
   static Type2() {
      Console.WriteLine("Type2's static ctor called");
   }
 
   // Use this attribute defined in the System.Runtime.ConstrainedExecution namespace
   [ReliabilityContract(Consistency.WillNotCorruptState, Cer.Success)]
   public static void M() { }
}
Now, when I run this version of the code, I get the following output:
Type2's static ctor called
In try

 

PrepareConstrainedRegions是一个特殊的方法，当编译器看到此方法在try模块前被调用，将优先执行try模块的catch和finally部分。