c#语法疑惑，求大佬

Question

using System;
namespace HelloWorldApplication
{
	
	class MyDate
	{
	    private double D1;
		private double D2;
		private double D3;
		
		public MyDate (double d1,double d2,double d3);
		{
		D1=d1;D2=d2;D3=d3;
		}
		public double Sum()
		{
		return D1+D2+D3;
		}
	}
	  class Ex
	{
	public double Av(MyDate md)
	{
	return md.Sum()/3;
	}
		  
	}
    class HelloWorld
    {
        static void Main(string[] args)
        {
			MyDate md =new MyDate(3,4,5);
			 Ex e =new Ex();   
            Console.WriteLine( "{0}",e.Av(md));
             
        }
    }
}

报错内容：Main.cs(12,3): error CS9010: Primary constructor body is not allowed
Compilation failed: 1 error(s), 0 warnings
Main.cs（12,3）：错误CS9010：不允许使用主构造函数主体
编译失败：1个错误，0个警告

理解不了这个报错的含义，求大佬指导

Answer 1

public MyDate (double d1,double d2,double d3);

后面多了个分号，去掉就可以了！