最近群里有个小伙伴把Dapper迁移SqlSugar几个不能解决的问题进行一个汇总,我正好写一篇文章来讲解一下
一、sql where in传参问题:
SELECT * FROM users where id IN @ids
答: SqlSugar中应该是
// SELECT * FROM users where id IN (@ids) var listdb.Ado.SqlQuery<Users>(sql,new {id=new int[]{1,2,3}})
二、Dapper查询出来的Dynamic动态类型,支持获取不存在的属性
例如:SELECT UserName FROM users
可以通过 result.UserCode,不会报错
答:dynamic expandobject 属性不存在肯定是会报错的 , list[0].id如果不存肯定报错
这个需求还是头一次,因为不报错可能不严谨SQLSugar暂时没有这个方法可以通扩展一个方法实现
using System.Collections.Generic; using System.Dynamic; public class ForgivingDynamicObject : DynamicObject { private readonly Dictionary<string, object> _members = new Dictionary<string, object>(); public override bool TryGetMember(GetMemberBinder binder, out object result) { // 尝试从字典中获取成员,如果不存在则返回null return _members.TryGetValue(binder.Name, out result) || (result = null) != null; } public override bool TrySetMember(SetMemberBinder binder, object value) { // 将成员设置到字典中 _members[binder.Name] = value; return true; } } public static class DynamicExtensions { public static ForgivingDynamicObject ToForgivingDynamicObject(this dynamic dynamicObject) { var forgivingObject = new ForgivingDynamicObject(); if (dynamicObject is IDictionary<string, object> dictionary) { foreach (var kvp in dictionary) { forgivingObject.TrySetMember(new SetMemberBinder(kvp.Key, false), kvp.Value); } } return forgivingObject; } } dynamic expando = new ExpandoObject(); expando.ExistingProperty = "Hello"; // 转换为 ForgivingDynamicObject ForgivingDynamicObject forgivingObj = expando.ToForgivingDynamicObject(); // 访问存在的属性 string value = forgivingObj.ExistingProperty; // "Hello" // 访问不存在的属性,将返回null而不是抛出异常 string nonExistingValue = forgivingObj.NonExistingProperty; // null
三、表值参数必须传typeName
Dapper是可以不用传的
Sqlsugar在5.4.1.152+ 下面value可以传null了
//SqlSugar中用法 var s = new SugarParameter("@p", value); s.TypeName = "dtTableName";
四、类型转换:在Dapper中很多类型做了兼容处理。
比如:数据库中是string,但值是int SELECT CAST( id as nvarchar) id FROM users
Dapper中Query实体时,id允许定义为string,
答:Sqlsugar中类型只支持int转string,不支持string转int
默认不支持反向转换考虑到数据严谨性,防止线上数据因错误数据导致系统出错
解决方案:加上特性让他支持转换
[SugarColumn(SqlParameterDbType=typeof(CommonPropertyConvert))]//ORM自带的也支持重写这个转换类 public DateTime DcValue { get; set; }
五、Dapper 联表VO转换
l 不支持IEnumerable<TReturn> Query<TFirst, TSecond, TReturn>(string sql, Func<TFirst, TSecond, TReturn> map, object? param = null, IDbTransaction? transaction = null, bool buffered = true, string splitOn = "Id", int? commandTimeout = null, CommandType? commandType = null) =>
MultiMap<TFirst, TSecond, DontMap, DontMap, DontMap, DontMap, DontMap, TReturn>(cnn, sql, map, param, transaction, buffered, splitOn, commandTimeout, commandType)
主要用于结果集返回之后,包装成一个有层次的对象。
Dapper执行ExecuteReader方法之后,还能通过Get<T>(“params”)获取到。SqlSugar是直接无法获取的,需要包装一次,从DataReaderParameters中获取。
答:
SqlSugar同样可以支持一维对象变成2维对象
var list=db.SqlQueryable<SQLVO>("select 1 as id,'jack' as name ").ToList(); public class SQLVO { [SugarColumn(IsOwnsOne =true)] public ITEM1 ITEM1 { get; set; }//item1和item2不能有重复字段 [SugarColumn(IsOwnsOne = true)] public ITEM2 ITEM2 { get; set; }//item1和item2不能有重复字段 } public class ITEM1 { public int ID { get; set; } } public class ITEM2 { public string Name { get; set; } }
效果图
标签:string,汇总,id,new,Dapper,null,public,SqlSugar From: https://www.cnblogs.com/sunkaixuan/p/18206516