声明结构体
struct abc
{
public string abc1;
public string abc2;
}
struct xyz
{
public string xyz1;
public string xyz2;
public abc a;
}

实例化
xyz x = new xyz();
x.xyz1 = "";
x.xyz2 = "";
x.a.abc1 = "";
x.a.abc2 = "";

class   test
{
static void Main(string[] args)
{
      xyz x = new xyz();
      x.s3 = "";
      x.s4 = "";
     x.a.s1 = "";
     x.a.s2 = "";
}
}

struct abc
{
public abc(int i)
{
      c1 = new char[4];
      s1 = "";
      s2 = "";
}
public char[] c1;
public string s1;
public string s2;
}
struct xyz
{
public string s3;
public string s4;
public abc a;
}