How to combine || operators in condition statement [duplicate]

Answer 1

You cannot do it this way. Instead you can do this:

string[] validValues = new string[] { "1", "5", "9", "whatever" };
if(validValues.Contains(foo))
{
    // do something
}

Answer 2

If you have multiple if conditions you should always consider using switch statements as compiler will create Jumptables whereever possible to increase speed. You should take a look here for speed test. Thing to note here is that if number of conditions is big enough to cover overheads, C# compiler will also create a HashTable object.

So this is a better approach,

switch (foo) {
case "1":
case "5":
case "9":
    // ...
    break;
case "2":
case "4":
    // ...
    break;
}

Answer 3

You may use the switch statement:

switch (foo) {
    case "1":
    case "5":
    case "9":
        // ...
        break;
    case "2":
    case "4":
        // ...
        break;
}

If foo is a string, pay attention on case sensitivity.

Answer 4

One possible option is this:

switch (foo)
{
    case "1":
    case "5":
    case "9":
        // your code here

        break;
}

Another possible option is this:

var vals = new string[] { "1", "5", "9" };
if (vals.Contains(foo))
{
    // your code here
}

Answer 5

You can do this, if that's acceptable to you:

if ( (new string[] {"1","9","5","6" }).Contains(foo))
{

}

Answer 6

If all options are just one character you could do:

if ("159".IndexOf(foo) != -1)
{
  //do something
}