.Net初使用MySql数据库生成Model类并与SqlServer简单对比

最近的一个项目，在.net中使用MySql数据库，背景是这样的：Sql Server要购买授权，每年100多万，本来公司这么大，这点钱也不算什么，但是领导说能省就省。对于技术人员来说，这是个挑战，时间紧，技术上还有未知的风险。想想从实习到现在，四年多的.Net研发了，都是用的Sql Server数据库，这个Mysql还是头一回用……

一、根据数据库生成EF的Model类
//表字段信息model

public class TableSchemaModel
{
/// <summary>
/// 表名
/// </summary>
public string TableName { get; set; }
/// <summary>
/// 字段名
/// </summary>
public string ColumnName { get; set; }
/// <summary>
/// 是否可空：可空-YES,不可空-NO
/// </summary>
public string IsNullable { get; set; }
/// <summary>
/// 字段数据类型
/// </summary>
public string DataType { get; set; }
/// <summary>
/// 字符串长度
/// </summary>
public int? CharacterMaximumLength { get; set; }
/// <summary>
/// 字段描述
/// </summary>
public string ColumnComment { get; set; }
/// <summary>
/// 键标识：主键-PRI,外键-MUL
/// </summary>
public string ColumnKey { get; set; }
}

public class TableRefrenceModel
{
/// <summary>
/// 表名
/// </summary>
public string TableName { get; set; }
/// <summary>
/// 字段名
/// </summary>
public string ColumnName { get; set; }
/// <summary>
/// 关联的表名
/// </summary>
public string ReferencedTableName { get; set; }
/// <summary>
/// 关联的表字段名
/// </summary>
public string ReferencedColumnName { get; set; }
}

//具体的处理方法，主要就是查询字段信息，循环生成Mode字段，就完了。

/// <summary>
/// 查询Mysql表字段信息
/// </summary>
/// <param name="tableName">表名</param>
/// <returns></returns>
public List<TableSchemaModel> GetTableSchemaData(string tableName)
{
List<TableSchemaModel> ret = null;
var tableSchema = dbContext.Database.Connection.Database;
string sql = string.Format("SELECT table_name TableName,column_Name ColumnName,is_nullable IsNullable,data_type DataType,character_maximum_length CharacterMaximumLength,column_comment ColumnComment,Column_Key ColumnKey FROM information_schema.COLUMNS WHERE table_schema='{0}' AND table_name = '{1}';", tableSchema, tableName);
ret = ExecuteQuerySql<TableSchemaModel>(sql);
return ret;
}
/// <summary>
/// 查询表中字段关联的所有外键表信息
/// </summary>
/// <param name="tableName"></param>
/// <returns></returns>
public List<TableRefrenceModel> GetTableRefrenceData(string tableName)
{
List<TableRefrenceModel> ret = null;
var tableSchema = dbContext.Database.Connection.Database;
string sql = string.Format("SELECT table_name TableName,column_name ColumnName,REFERENCED_TABLE_NAME ReferencedTableName,REFERENCED_COLUMN_NAME ReferencedColumnName FROM INFORMATION_SCHEMA.KEY_COLUMN_USAGE WHERE table_schema='{0}' AND table_name = '{1}';", tableSchema, tableName);
ret = ExecuteQuerySql<TableRefrenceModel>(sql);
return ret;
}

/// <summary>
/// 生成Model类文件中的非导航属性内容，到bin/Files 目录 的 tableName.cs文件
/// </summary>
/// <param name="tableName">表名，也是生成的Model类名</param>
public void GenerateModelJob(string tableName)
{
var data = taskRepository.GetTableSchemaData(tableName);
if (data != null)
{
var refrenceData = taskRepository.GetTableRefrenceData(tableName);
var priColumn = data.Where(o => o.ColumnKey == "PRI").First();
StringBuilder sb = new StringBuilder();
sb.Append(@"
namespace YCF.Stock.Core.Entities
{
using Abp.Domain.Entities;
using System;
using System.Collections.Generic;
using System.ComponentModel.DataAnnotations;
using System.ComponentModel.DataAnnotations.Schema;
using YCF.Stock.Core.Enum;

");
sb.AppendFormat("    [Table(\"{0}\")]", tableName).AppendLine();
sb.AppendFormat(@"    public partial class {0} : Entity<{1}>
", tableName, GetCSTypeFromDbType(priColumn.DataType)).Append("    {").AppendLine();
foreach (var field in data)
{
sb.AppendFormat(@"
/// <summary>
/// {0}
/// </summary>
", field.ColumnComment);

switch (field.DataType)
{
case "varchar":
case "nvarchar":
{
sb.AppendFormat(@"        [StringLength({0})]
[MaxLength({0})]
", field.CharacterMaximumLength);
}
break;
case "date":
case "bit":
{
sb.AppendFormat("        [Column(TypeName = \"{0}\")]", field.DataType).AppendLine();
}
break;
}
if (field.ColumnKey == "PRI")
{
sb.AppendFormat("        [Column(\"{0}\")]", field.ColumnName).AppendLine();
sb.AppendFormat("        public override {0} Id ", GetCSTypeFromDbType(field.DataType)).Append("{ get; set; }").AppendLine();
}
else
{
sb.AppendFormat("        public {0}{1} {2} ", GetCSTypeFromDbType(field.DataType), field.IsNullable == "YES" ? "?" : "", field.ColumnName).Append("{ get; set; }").AppendLine();
}
}
foreach (var refrence in refrenceData)
{
sb.AppendFormat("        public virtual {0} {0} ", refrence.ReferencedTableName).Append("{ get; set; }").AppendLine();
}
sb.Append(@"
}
}
");
var str = sb.ToString();
string saveDir = Path.Combine(AppDomain.CurrentDomain.BaseDirectory, "Files\\");
if (!Directory.Exists(saveDir)) Directory.CreateDirectory(saveDir);
string saveFilePath = System.IO.Path.Combine(saveDir, tableName + ".cs");
System.IO.File.AppendAllText(saveFilePath, str, Encoding.UTF8);
}
}

/// <summary>
/// Mysql数据库字段类型转化为C#字段类型
/// </summary>
/// <param name="dbType"></param>
/// <returns></returns>
private string GetCSTypeFromDbType(string dbType)
{
string ret = dbType;
switch (dbType)
{
case "nvarchar":
case "text":
case "varchar": ret = "string"; break;
case "datetime":
case "date": ret = "DateTime"; break;
case "bit": ret = "bool"; break;
case "bigint": ret = "long"; break;
}
return ret;
}

二、与Sql Server简单对比
1、从上面可以看到，查询MySql表结构的语句非常简单，全部的信息全部可以从information_schema.COLUMNS 这个对象里面查，还有外键表字段等等关联关系，全部都可以从INFORMATION_SCHEMA.KEY_COLUMN_USAGE对象查出来，只要传入指定的数据库名和表名就行了，相对 来说，Sql Server就复杂很多，如果一样要生成这个Model类，估计会非常头痛！

2、刚接触Mysql感觉有一些坑，比如存储过程的使用和Sql Server不一样、在.Net的EF中Mysql事务的使用和Sql Server不一样。最大的不同是，Mysql可以设置语句是否立即执行，如果没设置为true，在程序中调用SQL语句操作数据，都不会成功保存到数据库，后面都要加一个 commit; 才行。
现在用过一段时间，还行，有些东西注意一下就和sql server差不多。