String.Join Method (String, IEnumerable<String>)
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Updated: January 2011
Concatenates the members of a constructed IEnumerable<T> collection of type String, using the specified separator between each member.
Namespace: System
Assembly: mscorlib (in mscorlib.dll)
Syntax
'Declaration
<ComVisibleAttribute(False)> _
Public Shared Function Join ( _
separator As String, _
values As IEnumerable(Of String) _
) As String
[ComVisibleAttribute(false)]
public static string Join(
string separator,
IEnumerable<string> values
)
Parameters
- separator
Type: System.String
The string to use as a separator.
- values
Type: System.Collections.Generic.IEnumerable<String>
A collection that contains the strings to concatenate.
Return Value
Type: System.String
A string that consists of the members of values delimited by the separator string. If values has no members, the method returns String.Empty.
Exceptions
| Exception | Condition |
|---|---|
| ArgumentNullException | values is nulla null reference (Nothing in Visual Basic). |
Remarks
If separator is nulla null reference (Nothing in Visual Basic), an empty string (String.Empty) is used instead. If any member of values is nulla null reference (Nothing in Visual Basic), an empty string is used instead.
Join(String, IEnumerable<String>) is a convenience method that lets you concatenate each element in an IEnumerable(Of String) collection without first converting the elements to a string array. It is particularly useful with Language-Integrated Query (LINQ) query expressions. The following example passes a List(Of String) object that contains either the uppercase or lowercase letters of the alphabet to a lambda expression that selects letters that are equal to or greater than a particular letter (which, in the example, is "M"). The IEnumerable(Of String) collection returned by the Enumerable.Where method is passed to the Join(String, IEnumerable<String>) method to display the result as a single string.
Imports System.Collections.Generic
Imports System.Linq
Module Example
Public Sub Demo(ByVal outputBlock As System.Windows.Controls.TextBlock)
Dim output As String = String.Join(" ", GetAlphabet(True).Where(Function(letter) _
letter >= "M"))
outputBlock.Text &= output & vbCrLf
End Sub
Private Function GetAlphabet(ByVal upper As Boolean) As List(Of String)
Dim alphabet As New List(Of String)
Dim charValue As Integer = CInt(IIf(upper, 65, 97))
For ctr As Integer = 0 To 25
alphabet.Add(ChrW(charValue + ctr).ToString())
Next
Return alphabet
End Function
End Module
' The example displays the following output:
' M N O P Q R S T U V W X Y Z
using System;
using System.Collections.Generic;
using System.Linq;
public class Example
{
public static void Demo(System.Windows.Controls.TextBlock outputBlock)
{
string output = String.Join(" ", GetAlphabet(true).Where(letter =>
letter.CompareTo("M") >= 0));
outputBlock.Text += output + "\n";
}
private static List<string> GetAlphabet(bool upper)
{
List<string> alphabet = new List<string>();
int charValue = upper ? 65 : 97;
for (int ctr = 0; ctr <= 25; ctr++)
alphabet.Add(Convert.ToChar(charValue + ctr).ToString());
return alphabet;
}
}
// The example displays the following output:
// M N O P Q R S T U V W X Y Z
Examples
The following example uses the Sieve of Eratosthenes algorithm to calculate the prime numbers that are less than or equal to 100. It assigns the result to a List<T> object of type String, which it then passes to the Join(String, IEnumerable<String>) method.
Imports System.Collections.Generic
Module Example
Public Sub Demo(ByVal outputBlock As System.Windows.Controls.TextBlock)
Dim maxPrime As Integer = 101
Dim primes As List(Of String) = GetPrimes(maxPrime)
outputBlock.Text += String.Format("Primes less than {0}:", maxPrime) & vbCrLf
outputBlock.Text += String.Format(" {0}", String.Join(" ", primes)) & vbCrLf
End Sub
Private Function GetPrimes(ByVal maxPrime As Integer) As List(Of String)
Dim values(maxPrime) As Integer
' Use Sieve of Erathsthenes to determine prime numbers.
For ctr As Integer = 2 To _
CInt(Math.Ceiling(Math.Sqrt(values.GetUpperBound(0))))
If CInt(values.GetValue(ctr)) = 1 Then Continue For
For multiplier As Integer = ctr To maxPrime \ 2
If ctr * multiplier <= maxPrime Then values.SetValue(1, ctr * multiplier)
Next
Next
Dim primes As New List(Of String)
For ctr As Integer = 2 To values.GetUpperBound(0)
If CInt(values.GetValue(ctr)) = 0 Then primes.Add(ctr.ToString())
Next
Return primes
End Function
End Module
' The example displays the following output:
' Primes less than 100:
' 2 3 5 7 11 13 17 19 23 29 31 37 41 43 47 53 59 61 67 71 73 79 83 89 97
using System;
using System.Collections.Generic;
public class Example
{
public static void Demo(System.Windows.Controls.TextBlock outputBlock)
{
int maxPrime = 101;
List<int> primes = GetPrimes(maxPrime);
outputBlock.Text += String.Format("Primes less than {0}:", maxPrime) + "\n";
outputBlock.Text += String.Format(" {0}", String.Join(" ", primes)) + "\n";
}
private static List<int> GetPrimes(int maxPrime)
{
int[] values = new int[maxPrime + 1];
// Use Sieve of Erathsthenes to determine prime numbers.
for (int ctr = 2; ctr <= (int)Math.Ceiling(Math.Sqrt(values.GetUpperBound(0))); ctr++)
{
if ((int)values.GetValue(ctr) == 1) continue;
for (int multiplier = ctr; multiplier <= maxPrime / 2; multiplier++)
if (ctr * multiplier <= maxPrime)
values.SetValue(1, ctr * multiplier);
}
List<int> primes = new List<int>();
for (int ctr = 2; ctr <= values.GetUpperBound(0); ctr++)
if ((int)values.GetValue(ctr) == 0)
primes.Add(ctr);
return primes;
}
}
// The example displays the following output:
// Primes less than 100:
// 2 3 5 7 11 13 17 19 23 29 31 37 41 43 47 53 59 61 67 71 73 79 83 89 97
Version Information
Silverlight
Supported in: 5, 4
Silverlight for Windows Phone
Supported in: Windows Phone OS 7.1
Platforms
For a list of the operating systems and browsers that are supported by Silverlight, see Supported Operating Systems and Browsers.
Change History
Date |
History |
Reason |
|---|---|---|
January 2011 |
Noted that an empty string is substituted for any null member of the collection. |
Customer feedback. |