Check if a value is in an array (C#)
Question
How do I check if a value is in an array in C#?
Like, I want to create an array with a list of printer names.
These will be fed to a method, which will look at each string in turn, and if the string is the same as a value in an array, do that action.
For example:
string[] printer = {"jupiter", "neptune", "pangea", "mercury", "sonic"};
foreach (p in printer)
{
PrinterSetup(p);
}
These are the names of the printers, they are being fed to the PrinterSetup method.
PrinterSetup will look sort of like this (some pseudocode):
public void PrinterSetup(printer)
{
if (printer == "jupiter")
{
Process.Start("BLAH BLAH CODE TO ADD PRINTER VIA WINDOWS EXEC");
}
}
How do I format if (printer == "jupiter") in a way that C# can recognize?
Accepted Answer
Add necessary namespace
using System.Linq;
Then you can use linq Contains() method
string[] printer = {"jupiter", "neptune", "pangea", "mercury", "sonic"};
if(printer.Contains("jupiter"))
{
Process.Start("BLAH BLAH CODE TO ADD PRINTER VIA WINDOWS EXEC"");
}
Read more... Read less...
string[] array = { "cat", "dot", "perls" };
// Use Array.Exists in different ways.
bool a = Array.Exists(array, element => element == "perls");
bool b = Array.Exists(array, element => element == "python");
bool c = Array.Exists(array, element => element.StartsWith("d"));
bool d = Array.Exists(array, element => element.StartsWith("x"));
// Display bools.
Console.WriteLine(a);
Console.WriteLine(b);
Console.WriteLine(c);
Console.WriteLine(d);
----------------------------output-----------------------------------
1)True 2)False 3)True 4)False
Something like this?
string[] printer = {"jupiter", "neptune", "pangea", "mercury", "sonic"};
PrinterSetup(printer);
// redefine PrinterSetup this way:
public void PrinterSetup(string[] printer)
{
foreach (p in printer.Where(c => c == "jupiter"))
{
Process.Start("BLAH BLAH CODE TO ADD PRINTER VIA WINDOWS EXEC"");
}
}
public static bool Contains(Array a, object val)
{
return Array.IndexOf(a, val) != -1;
}
Note: The question is about arrays of strings. The mentioned routines are not to be mixed with the .Contains method of single strings.
I would like to add an extending answer referring to different C# versions and because of two reasons:
The accepted answer requires Linq which is perfectly idiomatic C# while it does not come without costs, and is not available in C# 2.0 or below. When an array is involved, performance may matter, so there are situations where you want to stay with Array methods.
No answer directly attends to the question where it was asked also to put this in a function (As some answers are also mixing strings with arrays of strings, this is not completely unimportant).
Array.Exists() is a C#/.NET 2.0 method and needs no Linq. Searching in arrays is O(n). For even faster access use HashSet or similar collections.
Since .NET 3.5 there also exists a generic method Array<T>.Exists() :
public void PrinterSetup(string[] printer)
{
if (Array.Exists(printer, x => x == "jupiter"))
{
Process.Start("BLAH BLAH CODE TO ADD PRINTER VIA WINDOWS EXEC");
}
}
You could write an own extension method (C# 3.0 and above) to add the syntactic sugar to get the same/similar ".Contains" as for strings for all arrays without including Linq:
// Using the generic extension method below as requested.
public void PrinterSetup(string[] printer)
{
if (printer.ArrayContains("jupiter"))
{
Process.Start("BLAH BLAH CODE TO ADD PRINTER VIA WINDOWS EXEC");
}
}
public static bool ArrayContains<T>(this T[] thisArray, T searchElement)
{
// If you want this to find "null" values, you could change the code here
return Array.Exists<T>(thisArray, x => x.Equals(searchElement));
}
In this case this ArrayContains() method is used and not the Contains method of Linq.
The elsewhere mentioned .Contains methods refer to List<T>.Contains (since C# 2.0) or ArrayList.Contains (since C# 1.1), but not to arrays itself directly.