Dapper学习 - Dapper.Rainbow - Update

Posted 2020-08-22 Sniper_ZL

上一篇介绍了Rainbow的Create方法, 这里就来介绍一下Update方法吧, 毕竟新增和修改是双胞兄弟嘛.

一、Update

1. 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.Update(i + 1, new
            {
                //BId = Guid.NewGuid().ToString(),
                //CreateDate = DateTime.Now,
                // IsDoublePosition = Convert.ToBoolean(i % 2),
                Name = "Xixi" + i,
                No = (i * 100 + i).ToString("000"),
                //Sex = i % 2
            });
        }
        db.CommitTransaction();
    }
    catch
    {
        db.RollbackTransaction();
        Console.WriteLine("Error happened");
    }
}

使用方法和Insert方法类似, Update方法由两个参数, 第一个参数是Id, 第二个参数是dynamic data, 如果你不想更新全部的列, 只需要新建一个实体, 里面只包含你想更新的列就行了, 这样做, 不会修改到别的列. 

结果:

 

2. 源码解析

/// <summary>
/// Update a record in the DB
/// </summary>
/// <param name="id"></param>
/// <param name="data"></param>
/// <returns></returns>
public int Update(TId id, dynamic data)
{
    List<string> paramNames = GetParamNames((object)data);

    var builder = new StringBuilder();
    builder.Append("update ").Append(TableName).Append(" set ");
    builder.AppendLine(string.Join(",", paramNames.Where(p => p != "Id").Select(p => p + "= @" + p)));
    builder.Append(" where " + "Id" + " = @Id");

    DynamicParameters parameters = new DynamicParameters(data);
    parameters.Add("Id", id);

    return database.Execute(builder.ToString(), parameters);
}

Dapper这里是通过反射传入参数data, 来提取其中的字段名称, 生成一个List<string>集合, 然后根据这个集合去拼接sql语句.

如果你的框架中, 数据库设计遵循的规则, 有CreateBy, CreateTime字段, 在我们获取到实体时, 就是Tch_Teacher的格式, 但是我们又不想再写一遍new{}, 或者dynamic obj = new ExpandoObject()的时候, 就可以从Update方法入手, 修改一下就可以省下许多事情.

 

 builder.AppendLine(string.Join(",", paramNames.Where(p => p != "Id" && p != "CreateBy" && p != "CreateTime").Select(p => p + "= @" + p)));

 

二、Delete

1. 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+=2)
        {
            var res = db.Teacher.Delete(i);
        }

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

删除方法就很简单了, Rainbow只提供了一个根据主键删除的方法, 这里可以扩展成Update的那种方式, 可以根据所传入的字段来匹配删除数据

 

2. 源码解析

先看Rainbow的源码, 这里就没有什么好说明的了

/// <summary>
/// Delete a record for the DB
/// </summary>
/// <param name="id"></param>
/// <returns></returns>
public bool Delete(TId id)
{
    return database.Execute("delete from " + TableName + " where " + "Id" + " = @id", new { id }) > 0;
}

下面来看一下, Delete的订制扩展方法

/// <summary>
/// 自定义删除方法
/// 根据传入字段来删除数据
/// </summary>
/// <param name="data"></param>
/// <returns></returns>
public bool Delete(dynamic data)
{
    List<string> paramNames = GetParamNames((object)data);
    var builder = new StringBuilder();
    builder.Append("delete from ").Append(TableName).Append(" where ");
    builder.Append(string.Join(" and ", paramNames.Select(n => n + "=@" + n)));
    return database.Execute(builder.ToString(), data) > 0;
}

这里的删除, 都是 and 连接, 如果想要 or , instr()>0 方式的, 那就只有自己写sql了, 这里并不提供此类方法

/// <summary>
/// Delete a record for the DB
/// </summary>
/// <param name="id"></param>
/// <returns></returns>
public bool DeleteWhere(string where, dynamic param = null)
{
    string wherestr = "";
    if (!string.IsNullOrEmpty(where))
        wherestr = " where " + where;
    return database.Execute("delete from " + TableName + wherestr, param) > 0;
}

可以自己写一个, 只要给条件就行了, 不过这个方法是有蛮大风险的, 如果where为空, 会清空表