DataTable转数组和数组转字符串

DataTable转数组：

string[] array=Array.ConvertAll<DataRow, string>(ds.Tables[0].Rows.Cast<DataRow>().ToArray(), r => r["ID"].ToString());

数组转字符串：

string[] array=["1","2","3","4"];

string arrayStr=string.join(',',array);

结果："1,2,3,4"