How add "or" in switch statements?

By stacking each switch case, you achieve the OR condition.

switch(myvar)
{
    case 2:
    case 5:
    ...
    break;

    case 7:
    case 12:
    ...
    break;
    ...
}

You may do this as of C# 9.0:

switch(myvar)
{
    case 2 or 5:
        // ...
        break;

    case 7 or 12:
        // ...
        break;
    // ...
}

case 2:
case 5:
do something
break;

You do it by stacking case labels:

switch(myvar)
{
    case 2:
    case 5:
    ...
    break;

    case 7: 
    case 12:
    ...
    break;
    ...
}

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