Check if a value is in an array (C#)
C#.NetArraysStringC# Problem Overview
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?
C# Solutions
Solution 1 - C#
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"");
}
Solution 2 - C#
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); // true
Console.WriteLine(b); // false
Console.WriteLine(c); // true
Console.WriteLine(d); // false
Solution 3 - C#
Add using System.Linq;
at the top of your file. Then you can do:
if ((new [] {"foo", "bar", "baaz"}).Contains("bar"))
{
}
Solution 4 - C#
public static bool Contains(Array a, object val)
{
return Array.IndexOf(a, val) != -1;
}
Solution 5 - C#
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"");
}
}
Solution 6 - C#
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.
Solution 7 - C#
You are just missing something in your method:
public void PrinterSetup(string printer)
{
if (printer == "jupiter")
{
Process.Start("BLAH BLAH CODE TO ADD PRINTER VIA WINDOWS EXEC"");
}
}
Just add string
and you'll be fine.
Solution 8 - C#
Not very clear what your issue is, but it sounds like you want something like this:
List<string> printer = new List<string>( new [] { "jupiter", "neptune", "pangea", "mercury", "sonic" } );
if( printer.Exists( p => p.Equals( "jupiter" ) ) )
{
...
}
Solution 9 - C#
Consider using HashSet<T>
Class for the sake of lookup performance:
> This method is an O(1) operation.
>
> — HashSet<T>.Contains
Method (T), MSDN.
For example:
class PrinterInstaller
{
private static readonly HashSet<string> PrinterNames = new HashSet<string>
{
"jupiter", "neptune", "pangea", "mercury", "sonic"
};
public void Setup(string printerName)
{
if (!PrinterNames.Contains(printerName))
{
throw new ArgumentException("Unknown printer name", "printerName");
}
// ...
}
}
Solution 10 - C#
I searched now over 2h to find a nicely way how to find duplicates in a list and how to remove them. Here is the simplest answer:
//Copy the string array with the filtered data of the analytics db into an list
// a list should be easier to use
List<string> list_filtered_data = new List<string>(analytics_db_filtered_data);
// Get distinct elements and convert into a list again.
List<string> distinct = list_filtered_data.Distinct().ToList();
The Output will look like this: Duplicated Elements will be removed in the new list called distinct!