SqlHelper简单实现（通过Expression和反射）7.MySql数据处理类

MySql的数据处理类和Sql Server没有太大差别，从思路上来说没有区别，所以此处只是给出代码，不再多加解释了。

 using System;
 using System.Configuration;
 using MySql.Data.MySqlClient;
 using RA.DataAccess.Common;

 namespace RA.DataAccess.MySqlDbUtility
 {
     public partial class DbUtility : IDbUtility
     {
         private MySqlConnection conn;
         private MySqlDataAdapter da;
         private readonly string connectionString;

         private DbUtility()
         {
             connectionString = ConfigurationManager.AppSettings["MySql"];
         }
         private static DbUtility _dbUtility;

         public static DbUtility GetInstance()
         {
             return _dbUtility ?? (_dbUtility = new DbUtility());
         }

         /// <summary>
         /// 为通过反射生成的实例赋值
         /// </summary>
         /// <typeparam name="T">实例的类型</typeparam>
         /// <param name="obj">实例</param>
         /// <param name="value">值</param>
         /// <param name="key">成员名称</param>
         private void SetValue<T>(ref T obj, Object value, String key) where T : class
         {
             var property = obj.GetType().GetProperty(key);
             var type = property.PropertyType.Name;
             if (value is System.DBNull)
             {
                 property.SetValue(obj, null, null);
                 return;
             }
             switch (type)
             {
                 case "Int32":
                     property.SetValue(obj, int.Parse(value.ToString()), null);
                     break;
                 case "String":
                     property.SetValue(obj, value.ToString(), null);
                     break;
                 case "DateTime":
                     property.SetValue(obj, (DateTime)value, null);
                     break;
                 default:
                     property.SetValue(obj, value, null);
                     break;
             }
         }
         /// <summary>
         /// 获得SQLSession实例
         /// </summary>
         /// <typeparam name="T"></typeparam>
         /// <returns></returns>
         public SqlSession<T> GetSqlExpression<T>() where T : class
         {
             var temp = new SqlSession<T>();
             conn = new MySqlConnection(connectionString);
             return temp;
         }
     }
 }

 using System;
 using System.Collections.Generic;
 using System.Data;
 using System.Linq;
 using System.Linq.Expressions;
 using MySql.Data.MySqlClient;
 using RA.DataAccess.Common;

 namespace RA.DataAccess.MySqlDbUtility
 {
     public partial class DbUtility
     {
         /// <summary>
         /// 获取列表，适用于单表查询
         /// </summary>
         /// <typeparam name="T"></typeparam>
         /// <param name="exp"></param>
         /// <returns></returns>
         public List<T> GetList<T>(SqlSession<T> exp) where T : class
         {
             var datatable = GetDataBySql<T>(exp.SqlExpression);
             var result = new List<T>();
             foreach (DataRow i in datatable.Rows)
             {
                 T obj = Activator.CreateInstance<T>();
                 foreach (var k in exp.Fields)
                 {
                     SetValue(ref obj, i[k], k);
                 }
                 result.Add(obj);
             }
             return result;
         }

         /// <summary>
         /// 获取列表，适用于联表查询
         /// </summary>
         /// <typeparam name="Target">DTO类型</typeparam>
         /// <typeparam name="T">exp代表的Entity类型</typeparam>
         /// <param name="exp">SQLSession实例</param>
         /// <returns>DTO列表</returns>
         public List<Target> GetList<Target, T>(SqlSession<T> exp) where T : class where Target : class
         {
             var datatable = GetDataBySql<T>(exp.SqlExpression);
             var result = new List<Target>();

             foreach (DataRow i in datatable.Rows)
             {
                 var obj = Activator.CreateInstance<Target>();
                 foreach (var k in EntityHelper.GetDTOFields<Target>())
                 {
                     SetValue(ref obj, i[k], k);
                 }
                 result.Add(obj);
             }
             return result;
         }

         public List<T> Paged<T>(Expression<Func<T, object>> By, int pageIndex, int pageSize = ) where T : class
         {
             var result = new List<T>();
             var sql = $@"SELECT * FROM {EntityHelper.GetTableName<T>()} ORDER BY {ExpressionHelper.GetSqlByExpression(By.Body)} LIMIT {pageIndex},{pageSize}";
             conn = new MySqlConnection(connectionString);
             conn.Open();
             var datatable = GetDataBySql<T>(sql);
             conn.Close();
             foreach (DataRow i in datatable.Rows)
             {
                 var obj = Activator.CreateInstance<T>();
                 foreach (var k in EntityHelper.GetFields<T>(false))
                 {
                     SetValue(ref obj, i[k], k);
                 }
                 result.Add(obj);
             }
             return result;
         }
         /// <summary>
         /// 按照主键获取单条记录
         /// </summary>
         /// <typeparam name="T">实体类型</typeparam>
         /// <param name="func">筛选条件</param>
         /// <returns>实体的实例</returns>
         public T GetSingle<T>(Expression<Func<T, bool>> func) where T : class
         {
             var temptable = new DataTable();
             var exp = ExpressionHelper.GetSqlByExpression(func.Body);
             var fields = EntityHelper.GetFiledString<T>();
             var tablename = EntityHelper.GetTableName<T>();
             var sql = "SELECT " + fields + " FROM " + tablename + " WHERE " + exp;
             conn = new MySqlConnection(connectionString);
             da = new MySqlDataAdapter(sql, conn);
             da.Fill(temptable);
             if(temptable.Rows.Count == )
             {
                 return null;
             }
             T obj = Activator.CreateInstance<T>();
             foreach (var k in EntityHelper.GetFields<T>(false))
             {
                 SetValue(ref obj, temptable.Rows[][k], k);
             }
             return obj;
         }

         /// <summary>
         /// 删除单个记录
         /// </summary>
         /// <typeparam name="T"></typeparam>
         /// <param name="func"></param>
         public int Delete<T>(Expression<Func<T, bool>> func) where T : class
         {
             var tablename = EntityHelper.GetTableName<T>();
             var exp = ExpressionHelper.GetSqlByExpression(func.Body);
             var sql = "DELETE FROM " + tablename + " WHERE " + exp;
             return RunSingleSql<T>(sql);
         }

         /// <summary>
         /// 添加单个记录
         /// </summary>
         /// <param name="obj"></param>
         public int Add<T>(T obj) where T : class
         {
             var data = ObjectHelper.GetKeyValue(obj);

             var sql = "INSERT INTO {0}({1}) VALUES({2})";
             var tablename = EntityHelper.GetTableName<T>();
             var keys = string.Join(",", data.Keys.ToArray());
             var values = string.Join(",", data.Values.Select(a => a == null ? "''" : "'" + a.ToString() + "'"));

             sql = string.Format(sql, tablename, keys, values);

             return RunSingleSql<T>(sql);
         }

         /// <summary>
         /// 执行除了Select以外的SQL，请不要在循环中使用这个方法，会有性能问题
         /// </summary>
         /// <typeparam name="T"></typeparam>
         /// <param name="sql"></param>
         /// <returns></returns>
         public int RunSingleSql<T>(string sql) where T : class
         {
             var conn = new MySqlConnection(connectionString);
             var dc = new MySqlCommand(sql, conn);

             if (conn.State != ConnectionState.Open)
             {
                 conn.Open();
             }
             try
             {
                 return dc.ExecuteNonQuery();
             }
             finally
             {
                 conn.Close();
             }
         }

         /// <summary>
         /// 通过sql获取数据
         /// </summary>
         /// <typeparam name="T"></typeparam>
         /// <param name="sql"></param>
         /// <returns></returns>
         public DataTable GetDataBySql<T>(string sql) where T : class
         {
             var conn = new MySqlConnection(connectionString);
             da = new MySqlDataAdapter(sql, conn);
             var result = new DataTable();
             da.Fill(result);
             return result;
         }

         /// <summary>
         /// 更新一条记录
         /// </summary>
         /// <typeparam name="T"></typeparam>
         /// <param name="obj">要修改的数据的Entity的实例</param>
         /// <param name="func">要修改数据的条件</param>
         /// <returns></returns>
         public int Update<T>(T obj, Expression<Func<T, bool>> func) where T : class
         {
             if (func == null)
             {
                 throw new ArgumentNullException("表达式不能为空！");
             }
             var tablename = EntityHelper.GetTableName<T>();
             var data = ObjectHelper.GetKeyValue(obj);
             var updatestr = data.Aggregate("", (current, i) => current + (i.Key + "='" + i.Value.ToString() + "',"));
             updatestr = updatestr.Substring(, updatestr.Length - );
             var where = ExpressionHelper.GetSqlByExpression(func.Body);
             var sql = $"UPDATE {tablename} SET {updatestr} WHERE {@where}";
             return RunSingleSql<T>(sql);
         }

         /// <summary>
         /// 批量添加记录
         /// </summary>
         /// <typeparam name="T"></typeparam>
         /// <param name="list"></param>
         public int AddList<T>(List<T> objs) where T : class
         {
             if (!objs.Any())
             {
                 throw new ArgumentNullException("列表为空！");
             }
             var tablename = EntityHelper.GetTableName(objs[].GetType());
             var conn = new MySqlConnection(connectionString);
             if (conn.State != ConnectionState.Open)
             {
                 conn.Open();
             }
             var transaction = conn.BeginTransaction();
             var dc = conn.CreateCommand();
             dc.Transaction = transaction;
             var count = ;
             try
             {
                 foreach (var k in objs)
                 {
                     var data = new Dictionary<string, object>();
                     foreach (var i in k.GetType().GetProperties())
                     {
                         var value = k.GetType().GetProperty(i.Name).GetValue(k, null);
                         data.Add(i.Name, value);
                     }
                     var keys = string.Join(",", data.Keys.ToArray());
                     var values = string.Join(",", data.Values.Select(a => "'" + a.ToString() + "'"));
                     var sql = $"INSERT INTO {tablename}({keys}) VALUES({values})";
                     dc.CommandText = sql;
                     dc.ExecuteNonQuery();
                     count++;
                 }
                 transaction.Commit();
                 return count;
             }
             catch (Exception ex)
             {
                 transaction.Rollback();
                 throw ex;
             }
             finally
             {
                 conn.Close();
             }
         }

         /// <summary>
         /// 获取总数
         /// </summary>
         /// <typeparam name="T"></typeparam>
         /// <param name="func">不传值的话，返回总数</param>
         /// <returns></returns>
         public int Count<T>(Expression<Func<T, bool>> func = null) where T : class
         {
             var tablename = EntityHelper.GetTableName<T>();
             var sql = "";
             if (func == null)
             {
                 sql = $"SELECT COUNT(*) FROM {tablename}";
             }
             else
             {
                 var where = ExpressionHelper.GetSqlByExpression(func.Body);
                 sql = $"SELECT COUNT(*) FROM {tablename} WHERE {@where}";
             }
             conn = new MySqlConnection(connectionString);
             da = new MySqlDataAdapter(sql, conn);
             var datatable = new DataTable();
             da.Fill(datatable);
             var result = (int)datatable.Rows[][];
             return result;
         }

         /// <summary>
         /// 获取单个值
         /// </summary>
         /// <typeparam name="T"></typeparam>
         /// <typeparam name="Target"></typeparam>
         /// <param name="field">字段名</param>
         /// <param name="func">条件表达式</param>
         /// <returns></returns>
         public Target Scala<T,Target>(Expression<Func<T, Target>> field,Expression<Func<T,bool>> func)
         {
             var fieldname = ExpressionHelper.GetSqlByExpression(field.Body);
             var exp = ExpressionHelper.GetSqlByExpression(func.Body);
             var sql = $"SELECT {fieldname} FROM {EntityHelper.GetTableName<T>()} WHERE {exp}";
             conn = new MySqlConnection(connectionString);
             da = new MySqlDataAdapter(sql, conn);
             var datatable = new DataTable();
             da.Fill(datatable);
             if(datatable.Rows.Count == )
             {
                 return default(Target);
             }
             var result = (Target)datatable.Rows[][];
             return result;
         }
     }
 }