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String.Join Method (String, Object())

Concatenates the elements of an object array, using the specified separator between each element.

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

'Declaration
<ComVisibleAttribute(False)> _
Public Shared Function Join ( _
	separator As String, _
	ParamArray values As Object() _
) As String

Parameters

separator
Type: System.String

The string to use as a separator. separator is included in the returned string only if values has more than one element.

values
Type: System.Object()

An array that contains the elements to concatenate.

Return Value

Type: System.String
A string that consists of the elements of values delimited by the separator string. If values is an empty array, the method returns String.Empty.

ExceptionCondition
ArgumentNullException

values is Nothing.

If separator is Nothing or if any element of values other than the first element is Nothing, an empty string (String.Empty) is used instead. See the Notes for Callers section if the first element of values is Nothing.

Join(String, Object()) is a convenience method that lets you concatenate each element in an object array without explicitly converting its elements to strings. The string representation of each object in the array is derived by calling that object's ToString method.

Notes to Callers

If the first element of values is Nothing, the Join(String, Object()) method does not concatenate the elements in values but instead returns String.Empty. A number of workarounds for this issue are available. The easiest is to assign a value of String.Empty to the first element of the array, as the following example shows.

Dim values() As Object = { Nothing, "Cobb", 4189, 11434, .366 }
If values(0) Is Nothing Then values(0) = String.Empty
Console.WriteLine(String.Join("|", values))
' The example displays the following output: 
'      |Cobb|4189|11434|0.366

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 integer array, which it then passes to the Join(String, Object()) method.

Module Example
   Public Sub Main()
      Dim maxPrime As Integer = 100
      Dim primes() As Integer = GetPrimes(maxPrime)
      Console.WriteLine("Primes less than {0}:", maxPrime)
      Console.WriteLine("   {0}", String.Join(" ", primes))
   End Sub 

   Private Function GetPrimes(maxPrime As Integer) As Integer()
      Dim values As Array = Array.CreateInstance(GetType(Integer), _
                              New Integer() { maxPrime - 1}, New Integer(){ 2 }) 
        ' Use Sieve of Eratosthenes to determine prime numbers. 
      For ctr As Integer = values.GetLowerBound(0) 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 System.Collections.Generic.List(Of Integer)
      For ctr As Integer = values.GetLowerBound(0) To values.GetUpperBound(0)
         If CInt(values.GetValue(ctr)) = 0 Then primes.Add(ctr)
      Next             
      Return primes.ToArray()
   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

.NET Framework

Supported in: 4.5.2, 4.5.1, 4.5, 4

.NET Framework Client Profile

Supported in: 4

Portable Class Library

Supported in: Portable Class Library

.NET for Windows Store apps

Supported in: Windows 8

.NET for Windows Phone apps

Supported in: Windows Phone 8.1, Windows Phone 8, Silverlight 8.1

Windows Phone 8.1, Windows Phone 8, Windows 8.1, Windows Server 2012 R2, Windows 8, Windows Server 2012, Windows 7, Windows Vista SP2, Windows Server 2008 (Server Core Role not supported), Windows Server 2008 R2 (Server Core Role supported with SP1 or later; Itanium not supported)

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

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