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String.Join Method (String, String[])

Updated: January 2011

Concatenates a specified separator String between each element of a specified String array, yielding a single concatenated string.

Namespace:  System
Assembly:  mscorlib (in mscorlib.dll)

public static string Join(
	string separator,
	string[] value


Type: System.String

A String.

Type: System.String[]

An array of String.

Return Value

Type: System.String
A String consisting of the elements of value interspersed with the separator string.


value is null.

For example if separator is ", " and the elements of value are "apple", "orange", "grape", and "pear", Join(separator, value) returns "apple, orange, grape, pear".

If separator is null, an empty string is used instead. If any element in value is null, an empty string is used instead.

The following example demonstrates the Join method.

using System;

public class JoinTest {
    public static void Main() {

        Console.WriteLine(MakeLine(0, 5, ", "));
        Console.WriteLine(MakeLine(1, 6, "  "));
        Console.WriteLine(MakeLine(9, 9, ": "));
        Console.WriteLine(MakeLine(4, 7, "< "));

    private static string MakeLine(int initVal, int multVal, string sep) {

        string [] sArr = new string [10];

        for (int i = initVal; i < initVal + 10; i++)
            sArr[i - initVal] = String.Format("{0,-3}", i * multVal);

        return String.Join(sep, sArr);

Windows 7, Windows Vista, Windows XP SP2, Windows XP Media Center Edition, Windows XP Professional x64 Edition, Windows XP Starter Edition, Windows Server 2008 R2, Windows Server 2008, Windows Server 2003, Windows Server 2000 SP4, Windows Millennium Edition, Windows 98, Windows CE, Windows Mobile for Smartphone, Windows Mobile for Pocket PC, Xbox 360, Zune

The .NET Framework and .NET Compact Framework do not support all versions of every platform. For a list of the supported versions, see .NET Framework System Requirements.

.NET Framework

Supported in: 3.5, 3.0, 2.0, 1.1, 1.0

.NET Compact Framework

Supported in: 3.5, 2.0, 1.0

XNA Framework

Supported in: 3.0, 2.0, 1.0




January 2011

Noted that an empty string is substituted for any null element in the array.

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