List转字符串，用逗号隔开

List<string> list = new List<string>();
list.Add("a");
list.Add("b");
list.Add("c");
//MessageBox.Show(list.);
//LoadModel();
string s = string.Join(",", list.ToArray());
MessageBox.Show(s);

List<test> list = new List<test>();
list.Add(new test("1", "a"));
list.Add(new test("2", "b"));
list.Add(new test("", ""));
list.Add(new test("3", "c"));
var a = from o in list select o.test1;
var b = from o in list select o.test2;
string s1 = string.Join(",", a.ToArray());
string s2 = string.Join(",", b.ToArray());
MessageBox.Show(s1 + "\r\n" + s2); 

结果：1,2,,3

      a,b,,c

字符串转List

这里s的分隔符不是“,”而是“， ”，后面有一个空格

string s = "1, 2, 3";
List<string> list = new List<string>(s.Split(new string[] { ", " }, StringSplitOptions.RemoveEmptyEntries));
foreach (string t in list)
{
    MessageBox.Show("*" + t + "*");
}

这里s的分隔符是“,”

string s = "1,2,3";
List<string> list = new List<string>(s.Split(‘,‘));
foreach (string t in list)
{
    MessageBox.Show("*" + t + "*");
}