以下两种方法之间有何区别？

Question

I have following code snippet.

bool b = false;
if (b) {}

but I have seen many people write something like:

if (true == b){}

They both look same to me, is there any difference here ?

Answer 1

bool b;
if (b) {}

You can't use this because C# compiler doesn't allow to use unassigned local variables.

On the other hand, there is no difference between

bool b = true;
if (b) {}

and

bool b = true;
if (true == b){}

They generate same MSIL code as well. But in my opinion, equality checking in second example is unnecessary. That's why if(b) seems cleaner than if(true == b) .

Answer 2

No, there is not a difference. (well, apart from the number of typed letters i suppose).

bool b = true; //ensure you initialise it though!! (if it was **C** you wouldn't think not to!)

So;

if(b)
{
 //doSomthing...
} 

means

if(true)
{
 //doSomething...
}

However,

if b was assigned to false, then the if statement would be skipped; like so:

bool b = false;
if(b)
{
//this won't be executed since b is false
}

---

As for your question, though, with you initialising b at the beginning, then yes, they would be the same

Answer 3

For me

if (true == b){}

is quite inelegant. Following that style in place of

if (a == b){}

you should put

if ((a == b) == true){}

and so on....

Answer 4

The if statement needs a boolean expression (the condition) to be true in order to execute the instructions inside its block. If you compare a boolean value to another boolean value you still get a boolean result, but, unless you are comparing two boolean variables with an unknown value, you may be writting a piece of useless code. To explain myself better:

bool a, b;

// some computation

if(a == b)
{
    // do stuff
}

makes sense, while

bool a;

// some computation

if(a == true)
{
    // do stuff
}

contains some useless code (in my opinion, it even loses some readability) because it is the equivalent of:

bool a;

// some computation

if(a)
{
    // do stuff
}

Answer 5

For the code:

bool b = true;
if (b) 
    Console.WriteLine("b-ok");
if (b==true)
    Console.WriteLine("b-true");

if we check the IL-CODE for the the first if

IL_000b:  ldloc.0
IL_000c:  ldc.i4.0
IL_000d:  ceq
IL_000f:  stloc.1
IL_0010:  ldloc.1            
IL_0011:  brtrue.s   IL_001e 
IL_0013:  ldstr      "b-ok"   
IL_0018:  call       void [mscorlib]System.Console::WriteLine(string)  
IL_001d:  nop

and for the second if

IL_001e:  ldloc.0
IL_001f:  ldc.i4.0
IL_0020:  ceq
IL_0022:  stloc.1
IL_0023:  ldloc.1
IL_0024:  brtrue.s   IL_0031
IL_0026:  ldstr      "b-true"
IL_002b:  call       void [mscorlib]System.Console::WriteLine(string)
IL_0031:  ....

We can clearly see that C# compiler produces the same IL code for both statements. Thus both approaches are totally same.