操作数据库(MySql)表的扩展方法类，对单表可以进行增、删、改、查。

最近在学ASP.NET MVC的时候，有的时候，要对进行增、删、改、查操作

一开始感觉用自己带的那个 ADO.NET Entity Data Model 来进行增、删，改、查挺方便的

但后来发一个问题，在MYSQL里不能同时在*.edmx打开多个Read操作，SQL里可以设置一个属性，不记得就可以了。

所以就不用它了，由于都是对单表进行操作，没有复杂的操作。

就写一个简单扩展方法

首先有一点就是，自己写的那个类的名称，必须和数据库里表的名称一至

要不能在进行增、删、改、查的时候，就会出问题了。

举个例子吧

//-->查询操作

var sp = new SortedParam[] { new SortedParam { FieldName = "id", Sorted = SortedType.Desc } };
user_info ui = new user_info();
var video = ui.ToList(sp, 30);   //-->获取用户信息，按 id 降序取出表中前三十条记录。

//-->插入操作

string errorMessage = string.Empty;
var ui = new user_info();
ui.Username = 'aaaa';
ui.Password = 'bbbb';
ui.Type = 1
var result=ui.Insert(null, ref errorMessage);
if(0< result )
{
//...
}
else
{
//...
}

//-->删除、修改基本上都差不多。

个人水平有限，如果更好的见记，还望各告诉。

具体的实例还是看看扩展方法。

扩展中使用到的两个类

1、排序用

/// <summary>
/// 排序类型
/// </summary>
public enum SortedType
{
/// <summary>
/// 升序
/// </summary>
Asc,
/// <summary>
/// 降序
/// </summary>
Desc
}
/// <summary>
/// 排序参数
/// </summary>
public class SortedParam
{
/// <summary>
/// 字段名称
/// </summary>
public string FieldName { get; set; }
/// <summary>
/// 排序类型
/// </summary>
public SortedType Sorted { get; set; }
}

2、条件用

/// <summary>
/// 字段参数
/// </summary>
public class FieldParam
{
/// <summary>
/// 字段名称
/// </summary>
public string FieldName { get; set; }
/// <summary>
/// 字段值
/// </summary>
public object FieldValue { get; set; }
/// <summary>
/// 字段类型
/// </summary>
public Type FieldType { get; set; }
}

操作数据库单表扩展方法

/// <summary>
/// 操作数据库单表扩展方法
/// </summary>
public static class AccessDBExtend
{
/// <summary>
/// 获取 T 表中记录集合
/// </summary>
/// <typeparam name="T">表的Model类</typeparam>
/// <param name="source">类的变量</param>
/// <returns>返回IList集合</returns>
public static IList<T> ToList<T>(this T source) where T : new()
{
string table = typeof(T).Name;
string sqlSentence = string.Format("select * from {0} ", table);
return DataTableToList<T>(sqlSentence);
}

/// <summary>
/// 获取 T 表中记录集合
/// </summary>
/// <typeparam name="T">表的Model类</typeparam>
/// <param name="source">类的变量</param>
/// <param name="pageSize">每页的大小</param>
/// <param name="pageIndex">当前页面索引</param>
/// <param name="total">当前表中记录总数</param>
/// <returns>返回IList集合</returns>
public static IList<T> ToList<T>(this T source, int pageSize, int pageIndex, out int total) where T : new()
{
return ToList<T>(source, null, null, pageSize, pageIndex, out total);
}

/// <summary>
/// 获取表的总数
/// </summary>
/// <param name="tableName">表的名称</param>
/// <param name="fields">条件</param>
/// <returns>返回记录数</returns>
static int GetTotal(string tableName, FieldParam[] fields)
{
string whereCondition = GetCondition(fields);
string sqlSentece = string.Format(" select count(*) from {0} {1} ", tableName, whereCondition);
return string.Format("{0}", DBAccess.ExecuteScalar(sqlSentece)).ConvertTo<int>();
}

/// <summary>
/// 获取 T 表中记录集合
/// </summary>
/// <typeparam name="T">表的Model类</typeparam>
/// <param name="source">类的变量</param>
/// <param name="fields">条件字段</param>
/// <param name="total">当前表中记录总数</param>
/// <returns>返回IList集合</returns>
public static IList<T> ToList<T>(this T source, FieldParam[] fields, out int total) where T : new()
{
return ToList<T>(source, fields, null, out total);
}

/// <summary>
/// 获取 T 表中记录集合
/// </summary>
/// <typeparam name="T">表的Model类</typeparam>
/// <param name="source">类的变量</param>
/// <param name="fields">条件字段</param>
/// <param name="sorted">排序</param>
/// <param name="total">当前表中记录总数</param>
/// <returns>返回IList集合</returns>
public static IList<T> ToList<T>(this T source, FieldParam[] fields, SortedParam[] sorted, out int total) where T : new()
{
string table = typeof(T).Name;
string sqlSentence = string.Format("select * from {0} {1} {2}", table, GetCondition(fields), GetOrderBy(sorted));
total = GetTotal(table, fields);
return DataTableToList<T>(sqlSentence);
}

/// <summary>
/// 获取 T 表中记录集合
/// </summary>
/// <typeparam name="T">表的Model类</typeparam>
/// <param name="source">类的变量</param>
/// <param name="fields">条件字段</param>
/// <param name="pageSize">每页的大小</param>
/// <param name="pageIndex">当前页面索引</param>
/// <param name="total">当前表中记录总数</param>
/// <returns>返回IList集合</returns>
public static IList<T> ToList<T>(this T source, FieldParam[] fields, int pageSize, int pageIndex, out int total) where T : new()
{
return ToList<T>(source, fields, null, pageSize, pageIndex, out total);
}

/// <summary>
/// 获取 T 表中记录集合
/// </summary>
/// <typeparam name="T">表的Model类</typeparam>
/// <param name="source">类的变量</param>
/// <param name="fields">条件字段</param>
/// <param name="sorted">排序</param>
/// <param name="pageSize">每页的大小</param>
/// <param name="pageIndex">当前页面索引</param>
/// <param name="total">当前表中记录总数</param>
/// <returns>返回IList集合</returns>
public static IList<T> ToList<T>(this T source, FieldParam[] fields, SortedParam[] sorted, int pageSize, int pageIndex, out int total) where T : new()
{
string table = typeof(T).Name;
string sqlSentence = GetSqlSentence(table, fields, sorted, pageSize, pageIndex);
total = GetTotal(table, fields);

List<String> item = new List<string>();
item.Add(string.Format("set @count = 0"));
item.Add(string.Format("set @count = 0"));
DBAccess.ExecuteNonQuery(item);
return DataTableToList<T>(sqlSentence);
}

/// <summary>
/// 获取 T 表中记录集合
/// </summary>
/// <typeparam name="T">表的Model类</typeparam>
/// <param name="source">类的变量</param>
/// <param name="sorted">排序</param>
/// <param name="pageSize">每页的大小</param>
/// <param name="pageIndex">当前页面索引</param>
/// <param name="total">当前表中记录总数</param>
/// <returns>返回IList集合</returns>
public static IList<T> ToList<T>(this T source, SortedParam[] sorted, int pageSize, int pageIndex, out int total) where T : new()
{
return ToList<T>(source, null, sorted, pageSize, pageIndex, out total);
}

/// <summary>
/// 获取 T 表中记录集合
/// </summary>
/// <typeparam name="T">表的Model类</typeparam>
/// <param name="source">类的变量</param>
/// <param name="sorted">排序</param>
/// <param name="topSize">获取表的前几条记录</param>
/// <returns>返回IList集合</returns>
public static IList<T> ToList<T>(this T source, SortedParam[] sorted, int topSize) where T : new()
{
string table = typeof(T).Name;
string orderBy = GetOrderBy(sorted);
string sqlSentence = string.Format("SELECT * from {0} {1} ", table, orderBy);
if (0 < topSize)
{
sqlSentence += string.Format(" LIMIT 0,{0} ", topSize);
}
return DataTableToList<T>(sqlSentence);
}

/// <summary>
/// 获取 T 表中记录集合
/// </summary>
/// <typeparam name="T">表的Model类</typeparam>
/// <param name="source">类的变量</param>
/// <param name="sorted">排序</param>
/// <returns>返回IList集合</returns>
public static IList<T> ToList<T>(this T source, SortedParam[] sorted) where T : new()
{
return ToList<T>(source,sorted,0);
}

/// <summary>
/// 将DataTable转成 IList
/// </summary>
/// <typeparam name="T"></typeparam>
/// <param name="sqlSentence"></param>
/// <returns></returns>
static IList<T> DataTableToList<T>(string sqlSentence) where T : new()
{
var dt = Database.DBAccess.GetDataTable(sqlSentence);
if (null == dt)
{
return null;
}
return dt.ToList<T>();
}

static string GetSqlSentence(string tableName, FieldParam[] fields, SortedParam[] sorted, int pageSize, int pageIndex)
{
string _orderBy = GetOrderBy(sorted);
string sql = string.Format("select * from (");
sql += string.Format("  SELECT (@count := @count +1) SerialNumber, t.* from {0} t {1} {2}", tableName, GetCondition(fields), _orderBy);

if (0 < pageSize)
{
sql += string.Format(" LIMIT 0,{0} ", pageSize * (pageIndex));
}
sql += string.Format(") v {0}", _orderBy);

if (0 < pageSize)
{
sql += string.Format(" LIMIT {0},{1}", pageSize * (pageIndex - 1), pageSize * (pageIndex));
}
return sql;
}

static string GetCondition(FieldParam[] fields)
{
if (null == fields || 0 == fields.Length)
{
return null;
}
string whereCondtion =
string.Format(" where {0}",
string.Join(" and ",
from p in fields
select string.Format("{0} = '{1}'", p.FieldName, p.FieldValue)));

return whereCondtion;
}

/// <summary>
///
/// </summary>
/// <param name="fields"></param>
/// <returns></returns>
static string GetOrderBy(SortedParam[] fields)
{
if (null == fields || 0 == fields.Length)
{
return null;
}
string whereCondtion =
string.Format(" order by {0}",
string.Join(" and ",
from p in fields
select string.Format("{0} {1}", p.FieldName, p.Sorted)));

return whereCondtion;
}

/// <summary>
/// 获取单条记录
/// </summary>
/// <typeparam name="T">表的Model类</typeparam>
/// <param name="source">类的变量</param>
/// <param name="fields">条件字段</param>
/// <returns>返回model类</returns>
public static T ToModel<T>(this T source, FieldParam[] fields) where T : new()
{
string table = typeof(T).Name;
string sqlSentence = string.Format("select * from {0} {1}", table, GetCondition(fields));
var dt = Database.DBAccess.GetDataTable(sqlSentence);
return dt.FirstModel<T>();
}

/// <summary>
/// 删除记录
/// </summary>
/// <typeparam name="T">表的Model类</typeparam>
/// <param name="source">类的变量</param>
/// <param name="fields">条件字段</param>
/// <returns>是否成功 , >0成功；否则失败。</returns>
public static int Delete<T>(this  T Source, FieldParam[] fields, ref string errorMessage)
{
try
{
string tableName = typeof(T).Name;
string sqlSentence = string.Format("delete from {0} {1} ", tableName, GetCondition(fields));
var result = DBAccess.ExecuteNonQuery(sqlSentence);
errorMessage = DBAccess.ErrorMessage;
return result;
}
catch (Exception ee)
{
errorMessage = ee.Message;
return -1;
}
}

/// <summary>
/// 向表中插入记录
/// </summary>
/// <typeparam name="T"></typeparam>
/// <param name="source"></param>
/// <param name="fields">不用进行插入的字符集合</param>
/// <param name="errorMessage"></param>
/// <returns></returns>
public static int Insert<T>(this T source, FieldParam[] fields, ref string errorMessage)
{
try
{
var tt = typeof(T);
string sqlSentence = GetInsertSentence<T>(source, fields);
var result = DBAccess.ExecuteNonQuery(sqlSentence);
errorMessage = DBAccess.ErrorMessage;
return result;
}
catch (Exception ee)
{
errorMessage = ee.Message;
return -1;
}
}

/// <summary>
/// 编辑，先删除，然后再进行插入操作，在一个事务里处理的【 0 成功；其它失败 】
/// </summary>
/// <typeparam name="T"></typeparam>
/// <param name="Source"></param>
/// <param name="fields"></param>
/// <returns></returns>
public static int Edit<T>(this T Source, FieldParam[] fields, ref string errorMessage)
{
try
{
string tableName = typeof(T).Name;
List<String> item = new List<string>();
string sqlSentence = string.Format("delete from {0} {1} ", tableName, GetCondition(fields));
item.Add(sqlSentence);
sqlSentence = GetInsertSentence<T>(Source, null);
item.Add(sqlSentence);

var result = DBAccess.ExecuteNonQuery(item);
errorMessage = DBAccess.ErrorMessage;
return result;
}
catch (Exception ee)
{
errorMessage = ee.Message;
return -1;
}
}

/// <summary>
/// 获取插入的SQL语句
/// </summary>
/// <typeparam name="T"></typeparam>
/// <param name="source"></param>
/// <param name="fields">不用插入的字符</param>
/// <returns></returns>
public static string GetInsertSentence<T>(this T source, FieldParam[] fields)
{
var tt = typeof(T);
List<String> fieldNames = new List<String>();
List<String> fieldValues = new List<String>();
var piItem = tt.GetProperties();
foreach (var v in piItem)
{
if (v.Name.ToLower().Equals("SerialNumber".ToLower()))
{
continue;
}
//-->判断是否存在fields
if (null != fields && 0 < fields.Length)
{
var fp = fields.Where(p => p.FieldName.ToLower().Equals(v.Name.ToLower())).GetFirst<FieldParam>();
if (null != fp)
{
continue;
}
}
fieldNames.Add(v.Name);
fieldValues.Add(GetPropertyValue(v, source));
}

string sql = string.Format("insert into {0} ({1}) values ({2}) ",
tt.Name,
string.Join(",", fieldNames),
string.Join(",", fieldValues));

return sql;
}

/// <summary>
/// 获取属性的值
/// </summary>
/// <param name="pi"></param>
/// <param name="source"></param>
/// <returns></returns>
static string GetPropertyValue(PropertyInfo pi, object source)
{
object value = pi.GetValue(source, null);
string result = string.Format(" '{0}' ", value);
switch (pi.PropertyType.FullName)
{
case "int":
case "int16":
case "int32":
case "int64":
case "System.UInt16":
case "System.UInt32":
case "System.UInt64":
case "System.Int16":
case "System.Int32":
case "System.Int64":
case "System.Single":
case "System.Double":
case "System.decimal":
result = string.Format(" {0} ", value);
break;
case "System.String":
value = Wrapper.StringReplace(string.Format("{0}", value));
result = string.Format(" '{0}' ", value);
break;
case "System.DateTime":
var dt = Convert.ToDateTime(value);
result = string.Format(" STR_TO_DATE('{0}','%Y-%m-%d %H:%i:%s') ", dt.ToString("yyyy-MM-dd HH:mm:ss"));
break;
}
return result;
}
}