C# Online Compiler | .NET Fiddle

// @nuget: Dapper -Version 1.60.6
using Dapper;
using System;
using System.Data.SqlClient;
using System.Linq;
					
public class Program
{
	public class Customer 
	{
		// 不存在无参构造函数，自动映射（默认显式转换）
		// 存在含参构造函数，查找对应类型，对应参数的构造函数（此处不会默认显式转换，比如枚举）
		// 对于 mysql tinyint(4) -> sbyte
		// 存在无参构造函数，无参构造函数会执行，但是以最终映射为准
		// 结论 -> Dapper Dto 如果需要含参构造函数，也要默认写一个无参构造函数
		//public Customer(){}
		
		public Customer(int customerID,string customerName,  long x)
		{
			CustomerID = customerID;
			CustomerName = customerName;
			X = x + 5;
		}
		public int CustomerID		{get;set;}
		public string CustomerName	{get;set;}
		
		public long X	{get;set;}
	}
	

	
	public static void Main()
	{
		Console.WriteLine(FiddleHelper.GetConnectionStringSqlServerW3Schools());
		string sql = "INSERT INTO Customers (CustomerName) Values (@CustomerName);";

		using (var connection = new SqlConnection(FiddleHelper.GetConnectionStringSqlServerW3Schools()))
		{
    		var affectedRows = connection.Execute(sql, new {CustomerName = "MarkX"});

    		Console.WriteLine(affectedRows);
			
			var customer = connection.Query<Customer>("Select CustomerID,CustomerName,1 AS X FROM CUSTOMERS WHERE CustomerName = 'MarkX'").ToList();
			
			FiddleHelper.WriteTable(customer);
		}
	}
}

 
// @nuget: Dapper -Version 1.60.6
using Dapper;
using System;
using System.Data.SqlClient;
using System.Linq;
                    
public class Program
{
    public class Customer 
    {
        // 不存在无参构造函数，自动映射（默认显式转换）
        // 存在含参构造函数，查找对应类型，对应参数的构造函数（此处不会默认显式转换，比如枚举）
        // 对于 mysql tinyint(4) -> sbyte
        // 存在无参构造函数，无参构造函数会执行，但是以最终映射为准
        // 结论 -> Dapper Dto 如果需要含参构造函数，也要默认写一个无参构造函数
        //public Customer(){}
        
        public Customer(int customerID,string customerName,  long x)
        {
            CustomerID = customerID;
            CustomerName = customerName;
            X = x + 5;
        }
        public int CustomerID       {get;set;}