.NET Framework 4.0新增了三個String.Join的多載函式Join(String, IEnumerable)、Join(String, IEnumerable)、與Join(String, Object[])。

這三個多載函式可以看出，我們可傳入Object[]、IEnumerable這三種新的型態，不需再將List、StringCollection等型態的資料塞成String[]就可以使用，也能在陣列中放入不同的型態，不需先將集合元素轉成字串，這部份在4.0(含)以後.NET Framework會幫我們做掉了。

完整的使用範例如下： using System; using System.Collections.Generic;

namespace ConsoleApplication1 { class Program { static void Main(string[] args) { String[] stringCollection = { “123”, “456”, “789” }; int[] intCollection = { 123, 456, 789 }; Object[] objCollection = { 123, “456”, 789.0f }; float[] floatCollection = { 123.0f, 456.0f, 789.0f };

ShowValue(“stringCollection”, stringCollection); ShowValue(“intCollection”, intCollection); ShowValue(“objCollection”, objCollection); ShowValue(“floatCollection”, floatCollection); }

static void ShowValue(string title, IEnumerable values) { Console.WriteLine("{0}: {1}", title, string.Join(",", values)); } } }

運行結果如下：

也可以整理成IEnumerable的擴充方法使用。

public static class IEnumerableExtension { public static string Join(this IEnumerable obj, string seperator) { return string.Join(seperator, obj); } }

這邊將上面的範例改為擴充方法的版本：

using System; using System.Collections.Generic;

namespace ConsoleApplication1 { class Program { static void Main(string[] args) { String[] stringCollection = { “123”, “456”, “789” }; int[] intCollection = { 123, 456, 789 }; Object[] objCollection = { 123, “456”, 789.0f }; float[] floatCollection = { 123.0f, 456.0f, 789.0f };

Console.WriteLine("{0}: {1}", “stringCollection”, stringCollection.Join(",")); Console.WriteLine("{0}: {1}", “intCollection”, intCollection.Join(",")); Console.WriteLine("{0}: {1}", “objCollection”, objCollection.Join(",")); Console.WriteLine("{0}: {1}", “floatCollection”, floatCollection.Join(",")); } }

public static class IEnumerableExtension { public static string Join(this IEnumerable obj, string seperator) { return string.Join(seperator, obj); } } }

String.Join 方法