I'm doing an C# app where I use
if ((message.Contains("test")))
{
Console.WriteLine("yes");
} else if ((message.Contains("test2"))) {
Console.WriteLine("yes for test2");
}
There would be any way to change to switch()
the if()
statements?
This question is related to
c#
string
if-statement
switch-statement
contains
Simple yet efficient with c#
string sri = "Naveen";
switch (sri)
{
case var s when sri.Contains("ee"):
Console.WriteLine("oops! worked...");
break;
case var s when sri.Contains("same"):
Console.WriteLine("oops! Not found...");
break;
}
Correct final syntax for [Mr. C]s answer.
With the release of VS2017RC and its C#7 support it works this way:
switch(message)
{
case string a when a.Contains("test2"): return "no";
case string b when b.Contains("test"): return "yes";
}
You should take care of the case ordering as the first match will be picked. That's why "test2" is placed prior to test.
switch(message)
{
case "test":
Console.WriteLine("yes");
break;
default:
if (Contains("test2")) {
Console.WriteLine("yes for test2");
}
break;
}
string message = "This is test1";
string[] switchStrings = { "TEST1", "TEST2" };
switch (switchStrings.FirstOrDefault<string>(s => message.ToUpper().Contains(s)))
{
case "TEST1":
//Do work
break;
case "TEST2":
//Do work
break;
default:
//Do work
break;
}
Some custom swtich can be created like this. Allows multiple case execution as well
public class ContainsSwitch
{
List<ContainsSwitch> actionList = new List<ContainsSwitch>();
public string Value { get; set; }
public Action Action { get; set; }
public bool SingleCaseExecution { get; set; }
public void Perform( string target)
{
foreach (ContainsSwitch act in actionList)
{
if (target.Contains(act.Value))
{
act.Action();
if(SingleCaseExecution)
break;
}
}
}
public void AddCase(string value, Action act)
{
actionList.Add(new ContainsSwitch() { Action = act, Value = value });
}
}
Call like this
string m = "abc";
ContainsSwitch switchAction = new ContainsSwitch();
switchAction.SingleCaseExecution = true;
switchAction.AddCase("a", delegate() { Console.WriteLine("matched a"); });
switchAction.AddCase("d", delegate() { Console.WriteLine("matched d"); });
switchAction.AddCase("a", delegate() { Console.WriteLine("matched a"); });
switchAction.Perform(m);
Nope, switch statement requires compile time constants. The statement message.Contains("test")
can evaluate true or false depending on the message so it is not a constant thus cannot be used as a 'case' for switch statement.
If you just want to use switch/case
, you can do something like this, pseudo-code:
string message = "test of mine";
string[] keys = new string[] {"test2", "test" };
string sKeyResult = keys.FirstOrDefault<string>(s=>message.Contains(s));
switch (sKeyResult)
{
case "test":
Console.WriteLine("yes for test");
break;
case "test2":
Console.WriteLine("yes for test2");
break;
}
But if the quantity of keys is a big, you can just replace it with dictionary, like this:
static Dictionary<string, string> dict = new Dictionary<string, string>();
static void Main(string[] args)
{
string message = "test of mine";
// this happens only once, during initialization, this is just sample code
dict.Add("test", "yes");
dict.Add("test2", "yes2");
string sKeyResult = dict.Keys.FirstOrDefault<string>(s=>message.Contains(s));
Console.WriteLine(dict[sKeyResult]); //or `TryGetValue`...
}
Stegmenn nalied it for me but I had one change for when you have an IEnumerbale instead of a string = message like in his example.
private static string GetRoles(IEnumerable<External.Role> roles)
{
string[] switchStrings = { "Staff", "Board Member" };
switch (switchStrings.FirstOrDefault<string>(s => roles.Select(t => t.RoleName).Contains(s)))
{
case
"Staff":
roleNameValues += "Staff,";
break;
case
"Board Member":
roleNameValues += "Director,";
break;
default:
break;
}
This will work in C# 8 using a switch expresion
var message = "Some test message";
message = message switch
{
string a when a.Contains("test") => "yes",
string b when b.Contains("test2") => "yes for test2",
_ => "nothing to say"
};
For further references https://docs.microsoft.com/en-us/dotnet/csharp/language-reference/operators/switch-expression
This will work in C# 7. As of this writing, it has yet to be released. But if I understand this correctly, this code will work.
switch(message)
{
case Contains("test"):
Console.WriteLine("yes");
break;
case Contains("test2"):
Console.WriteLine("yes for test2");
break;
default:
Console.WriteLine("No matches found!");
}
Source: https://blogs.msdn.microsoft.com/dotnet/2016/08/24/whats-new-in-csharp-7-0/
Faced with this issue when determining an environment, I came up with the following one-liner:
string ActiveEnvironment = localEnv.Contains("LIVE") ? "LIVE" : (localEnv.Contains("TEST") ? "TEST" : (localEnv.Contains("LOCAL") ? "LOCAL" : null));
That way, if it can't find anything in the provided string that matches the "switch" conditions, it gives up and returns null
. This could easily be amended to return a different value.
It's not strictly a switch, more a cascading if statement but it's neat and it worked.
Source: Stackoverflow.com