c# 字符串数组元素合并成一个字符串

string[] sa={"2","333"}
String.join("",aa)

static void Main(string[] args)
{
char[] y = { 'a', 'b', 'c', 'd', ' ' };
Console.WriteLine(y);
for (int i = 1; i < 4; i++)
{
char[] x = { 'a', 'b', 'c', 'd', ' ' };
for (int j = 3; j>=i; j--)
{
x[j+1] = x[j];
}
x[i] = ' ';
Console.WriteLine(x);
}
Console.ReadLine();
}