Dapper学习

Dapper这个ORM有许多扩展, 我自己用过两种, 也算是比较主流的两种, Rainbow和Extension, 这里就先介绍下Rainbow吧, 毕竟这个先用, 当然, 由于我使用的是mysql数据库(项目中, java和.net结合的, 所以mssql用不了, 就用了mysql), 所以在使用Rainbow插件的时候, 需要修改一下, 这个不是针对mysql的.

由于时间关系, 先来介绍一下Create吧, 万丈高楼Create起.

项目中下载Dapper.Rainbow的方法: PM>install-package dapper.rainbow

一、Create

在引用了下载后的程序集, 就可以开始编码了

public class Rainbow : Database<Rainbow>
{
    public Table<Tch_Teacher> Teacher { get; set; }

    public Table<Tch_Contact> Contact { get; set; }
}

还是之前的那几个类, 结构和名称都没有变.

测试代码:

var conStr = ConfigurationManager.ConnectionStrings["Cons"].ToString();
using (var conn = new MySqlConnection(conStr))
{
    var db = Rainbow.Init(conn, 2000);

    try
    {
        db.BeginTransaction();

        for (int i = 0; i < 10; i++)
        {
            var res = db.Teacher.Insert(new Tch_Teacher()
            {
                BId = Guid.NewGuid().ToString(),
                CreateDate = DateTime.Now,
                IsDoublePosition = false,
                Name = "Haha" + i,
                No = i.ToString("000"),
                Sex = i % 2
            });
        }

        db.CommitTransaction();
    }
    catch
    {
        db.RollbackTransaction();
        Console.WriteLine("Error happened");
    }
}
Console.ReadKey();

结果:

二、源码解析

/// <summary>
/// Insert a row into the db
/// </summary>
/// <param name="data">Either DynamicParameters or an anonymous type or concrete type</param>
/// <returns></returns>
public virtual int Insert(dynamic data)
{
    var o = (object)data;
    //获取字段/属性 名称
    List<string> paramNames = GetParamNames(o); 
    //去除Id, Rainbow默认每个表都有自增主键Id
    paramNames.Remove("Id");

    string cols = string.Join(",", paramNames); //BId,CreateDate,IsDoublePosition,Name,No,Sex
    string cols_params = string.Join(",", paramNames.Select(p => "@" + p));//@BId,@CreateDate,@IsDoublePosition,@Name,@No,@Sex

    //var sql = "set nocount on insert " + TableName + " (" + cols + ") values (" + cols_params + ") select cast(scope_identity() as int)";  原Rainbow语句

    //修改部分
    var sql = "insert " + TableName + " (" + cols + ") values (" + cols_params + ");SELECT LAST_INSERT_ID() AS LastInsertedId";

    return database.Query<int>(sql, o).Single();
}

当LastInsertedId为null的时候, 会返回0, 并不影响结果

internal static List<string> GetParamNames(object o)
{
    if (o is DynamicParameters)
    {
        return (o as DynamicParameters).ParameterNames.ToList();
    }

    List<string> paramNames;
    if (!paramNameCache.TryGetValue(o.GetType(), out paramNames))
    {
        paramNames = new List<string>();
        foreach (var prop in o.GetType().GetProperties(BindingFlags.GetProperty | BindingFlags.Instance | BindingFlags.Public))
        {
            var attribs = prop.GetCustomAttributes(typeof(IgnorePropertyAttribute), true);
            var attr = attribs.FirstOrDefault() as IgnorePropertyAttribute;
            if (attr == null || (attr != null && !attr.Value))
            {
                paramNames.Add(prop.Name);
            }
        }
        paramNameCache[o.GetType()] = paramNames;
    }
    return paramNames;
}

从上面的代码可以看到, 如果不想更新某些字段, 可以在字段上面加上特性[IgnoreProperty], 还可以看到Insert的参数, 是一个动态对象, 不一定非得是Tch_Teacher, 也可以是别的类型, 例如 new {BId="111"}(我常用)形式的.