001 SqlSugar 查詢擴展
博客園Id:13041713
提出問題
有的時候我們在進行單表查詢時,可能需要的條件有很多,但是,我們需要一一來判斷,查詢參數是否爲空,如果爲空就不使用這個字段來作爲查詢條件,在這種情況下,我們會寫大量的if語句
,這是一種重複的工作,我們應該如何避免這樣的問題呢?
下面是重複代碼的示例程序代碼:
/// <summary>
/// 加載登錄信息
/// </summary>
/// <returns></returns>
public IActionResult LoadAllLoginInfo(LoginInfoReqDto loginInfoReqDto)
{
var totalCount = 0;
var querySqlQueryable = this._context.Queryable<sys_loginfo>();
if (!string.IsNullOrEmpty(loginInfoReqDto.LoginName))
{
querySqlQueryable = querySqlQueryable.Where(x => x.loginname == loginInfoReqDto.LoginName);
}
if (!string.IsNullOrEmpty(loginInfoReqDto.LoginIp))
{
querySqlQueryable = querySqlQueryable.Where(x => x.loginip == loginInfoReqDto.LoginIp);
}
if (loginInfoReqDto.StartTime != DateTime.MinValue)
{
querySqlQueryable = querySqlQueryable.Where(x => x.logintime >= loginInfoReqDto.StartTime);
}
if (loginInfoReqDto.EndTime != DateTime.MinValue)
{
querySqlQueryable = querySqlQueryable.Where(x => x.logintime <= loginInfoReqDto.EndTime);
}
var queryResult = querySqlQueryable.OrderBy(x => x.id, OrderByType.Desc)
.ToPageList(loginInfoReqDto.Page, loginInfoReqDto.Limit, ref totalCount);
var result = new LoginInfoResDto
{
Code = 0,
Msg = "查詢成功",
Count = totalCount,
Data = queryResult
};
return Json(result);
}#
上面代碼中,我們可以看到有很多拼裝表達式樹的過程代碼. 這樣的話,往往需要我們寫很多無意義的冗餘代碼.
下面我們把代碼精簡一下.
簡化代碼如下:
/// <summary>
/// 加載登錄信息
/// </summary>
/// <returns></returns>
public IActionResult LoadAllLoginInfo(LoginInfoReqDto loginInfoReqDto)
{
var totalCount = 0;
var querySqlQueryable = this._context.Queryable<sys_loginfo>();
querySqlQueryable = this._context.Queryable<sys_loginfo>().Where(loginInfoReqDto);
var queryResult = querySqlQueryable.OrderBy(x => x.id, OrderByType.Desc)
.ToPageList(loginInfoReqDto.Page, loginInfoReqDto.Limit, ref totalCount);
var result = new LoginInfoResDto
{
Code = 0,
Msg = "查詢成功",
Count = totalCount,
Data = queryResult
};
return Json(result);
}
通過上面的代碼,我們簡化了很多不需要的if
語句拼裝表達式樹的過程.
核心SqlSugar查詢擴展
代碼如下:
using System.Collections.Generic;
using System.Text;
using System.Reflection;
namespace SqlSugar
{
public static class SqlSugarExt
{
/// <summary>
/// 根據條件對象查詢數據
/// </summary>
/// <typeparam name="T">表實體對象</typeparam>
/// <param name="sugarQueryable">sugar查詢對象</param>
/// <param name="whereObj">查詢實體</param>
/// <returns></returns>
public static ISugarQueryable<T> Where<T>(this ISugarQueryable<T> sugarQueryable, object whereObj)
{
var sugarQueryableWhere = sugarQueryable;
var whereObjType = whereObj.GetType();
var whereDic = new Dictionary<string, object>(); //裝載where條件
var inDic = new Dictionary<string,List<int>>(); //裝載in條件
foreach (var property in whereObjType.GetProperties())
{
var curName = property.Name;
if (property.PropertyType.Name.Equals("List`1")) //集合
{
var curValue = property.GetValue(whereObj, null);
inDic.Add(curName, (List<int>)curValue);
}
else
{
var curValue = property.GetValue(whereObj, null);
if (curValue==null) continue; //排除參數值爲null的查詢條件
whereDic.Add(curName.ToLower(), curValue);
}
}
var dbModelType = typeof(T);
var expSb = new StringBuilder();
foreach (var property in dbModelType.GetProperties()) //遍歷dbModel屬性
{
foreach (var (key, value) in whereDic)
{
if (property.Name.ToLower() != key) continue;
expSb.Append(ProcessExp(property,value)); //拼接where條件
expSb.Append(" and ");
}
}
if (expSb.Length != 0) //轉換where條件表達式樹
{
var exp = expSb.ToString().Remove(expSb.Length - 4, 4);
var e = System.Linq.DynamicCore.DynamicExpression.ParseLambda<T, bool>(exp);
sugarQueryableWhere = sugarQueryable.Where(e);
}
if (inDic.Count == 0) return sugarQueryableWhere;
foreach (var (key, value) in inDic) //轉換in條件表達式樹
{
var e2 = System.Linq.DynamicCore.DynamicExpression.ParseLambda<T, object>(key);
sugarQueryableWhere = sugarQueryableWhere.In(e2, value);
}
return sugarQueryableWhere;
}
/// <summary>
/// 處理表達式樹拼接
/// </summary>
/// <param name="property"></param>
/// <param name="value"></param>
/// <returns></returns>
private static string ProcessExp(PropertyInfo property,object value)
{
//引用類型 此處只考慮string類型的情況
if (!property.PropertyType.IsValueType) return $"{property.Name} = \"{value}\" ";
//可空值類型 此處只考慮簡單值類型
if (property.PropertyType.Name.Equals("Nullable`1"))
{
if (property.PropertyType.GenericTypeArguments[0].Name.Equals("DateTime"))
{
return $"{property.Name} = Convert.ToDateTime(\"{value}\") ";
}
return $"{property.Name} = {value} ";
}
//值類型 此處只考慮簡單值類型
if (property.PropertyType.Name.Equals("DateTime"))
{
return $"{property.Name} = Convert.ToDateTime(\"{value}\") ";
}
return $"{property.Name} = {value} ";
}
}
}
以上代碼需要在項目中,引入如下程序集:
開源代碼下載地址 請根據使用的項目,自行選擇編譯指定項目,後獲取dll,導入到自己的項目中.