Array.ConvertAllメソッドを使って配列内の全ての値を変換する
Imports System

Class Sample
  ' 度数を弧度に変える
  Shared Function ToRadian(ByVal degree As Double) As Double
    Return degree * Math.PI / 180.0
  End Function

  Shared Sub Main()
    Dim degrees() As Double = {0.0, 90.0, 180.0, 270.0}

    ' 配列内の値をすべて弧度に変換する
    Dim radians() As Double = Array.ConvertAll(degrees, AddressOf ToRadian)

    For Each rad As Double In radians
      Console.Write("{0}, ", rad)
    Next
    Console.WriteLine()

    ' 配列を文字列の配列に変換して連結する
    Console.WriteLine(String.Join(", ", Array.ConvertAll(degrees, AddressOf Convert.ToString)))
  End Sub
End Class
実行結果
0, 1.5707963267949, 3.14159265358979, 4.71238898038469, 
0, 90, 180, 270