Question

C# .NET 3.5. I’m trying to understand the intrinsic limitation of the C# Action object. Within the lamda (are those, in fact, lamdas?), we can perform assignments, call functions, even execute a ternary operation, but we can’t execute a multi-statement operation.

Is this because the single-statement execution is just syntactic sugar for wrapping it in a delegate? Why does the first example below not work?

public class MyClass {     private int m_Count = 0;      public void Test()     {         int value = 0;          // Does not work, throws compile error         Action action = () => { if(m_Count < 10) m_Count++; value = m_Count; }          // Works         Action action2 = () => value = delegate(){              if(m_Count < 10)                  m_Count++;               return m_Count;         };          // Works         Action action3 = () => value = m_Count;          // Works         Action action4 = () => value = m_Count < 10 ? m_Count++ : 0;          // Works         Action action5 = () => value = Increment();     }      public int Increment()     {         if (m_Count < 10)             m_Count++;          return m_Count;     } } 

EDIT: Grr, sorry for the noise. Originally, I had

Action action = () => if(m_Count < 10) m_Count++; value = m_Count; 

Which threw a compile error, but then right before the post I thought I’d try wrapping it in braces

Action action = () => { if(m_Count < 10) m_Count++; value = m_Count; } 

Which also threw a compile error, so I jumped to conclusions that it was the same problem. It works, though, if I toss in a semi-colon after the braces

Action action = () => { if(m_Count < 10) m_Count++; value = m_Count; }; 

Sorry for the noise!

EDIT 2: Thanks cfeduke, you posted that at the same time as my edit above – went ahead and marked as answer.

Answer 1

You are missing a semi-colon, it compiles:

 Action action = () => { if (m_Count < 10) m_Count++; value = m_Count; }; 

When you say type name = statement; you need a semicolon even if you use braces for a code block.