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什么都2020了,LINQ查询你还在用表达式树

1、简介

今天给大家推荐个好的轮子,System.Linq.Dynamic.Core。我们都知道

数据库应用程序经常依赖于“动态SQL”,即在运行时通过程序逻辑构造的查询。拼接SQL容易造成SQL注入,普通的LINQ可以用表达式树来完成,但也比较麻烦。推荐System.Linq.Dynamic.Core用起来比较方便。

这是Microsoft程序集的.NET 4.0动态语言功能的.NET Core /标准端口。

什么都2020了,LINQ查询你还在用表达式树

使用此库,可以在iQueryTable上编写动态LINQ查询(基于字符串):

var query = db.Customers     .Where("City == @0 and Orders.Count >= @1", "London", 10)     .OrderBy("CompanyName")     .Select("new(CompanyName as Name, Phone)");

2、使用

2.1、nuget

 

Install-Package System.Linq.Dynamic.Core -Version 1.2.5

2.2、常见方式

using System.Collections; using System.Collections.Generic; using System.Linq.Dynamic.Core.Tests.Helpers; using System.Linq.Dynamic.Core.Tests.Helpers.Models; using System.Linq.Expressions; using System.Reflection;  namespace System.Linq.Dynamic.Core.ConsoleTestApp {     public static class E     {         public static IQueryable GroupBy2<TSource, TKey>(this IQueryable<TSource> source, Expression<Func<TSource, TKey>> keyLambda2)         {             //LambdaExpression keyLambda = DynamicExpression.ParseLambda(source.ElementType, null, "new (Profile.Age)", null);             LambdaExpression x = (LambdaExpression)keyLambda2;              //return source.Provider.CreateQuery<IGrouping<TKey, TSource>>(             //    Expression.Call(             //        typeof(Queryable), "GroupBy",             //        new Type[] { source.ElementType, keySelector.Body.Type },             //        new Expression[] { source.Expression, Expression.Quote(keySelector) }             //        ));               return source.Provider.CreateQuery(                Expression.Call(                    typeof(Queryable), "GroupBy",                    new Type[] { source.ElementType, x.Body.Type },                    new Expression[] { source.Expression, Expression.Quote(x) }));         }     }      public class Program {         public static void Main(string[] args)         {             Console.WriteLine("--start");              DynamicProperty[] props = { new DynamicProperty("Name", typeof(string)), new DynamicProperty("Birthday", typeof(DateTime)) };             Type type = DynamicClassFactory.CreateType(props);              DynamicProperty[] props2 = { new DynamicProperty("Name", typeof(string)), new DynamicProperty("Birthday", typeof(DateTime)) };             Type type2 = DynamicClassFactory.CreateType(props2);              DynamicProperty[] props3 = { new DynamicProperty("Name", typeof(int)), new DynamicProperty("Birthday", typeof(DateTime)) };             Type type3 = DynamicClassFactory.CreateType(props3);                          DynamicClass dynamicClass = Activator.CreateInstance(type) as DynamicClass;             dynamicClass.SetDynamicPropertyValue("Name", "Albert");             dynamicClass.SetDynamicPropertyValue("Birthday", new DateTime(1879, 3, 14));             Console.WriteLine(dynamicClass);              string n1 = dynamicClass["Name"] as string;             Console.WriteLine("dynamicClass["Name"] = '" + n1 + "'");              dynamicClass["NameX"] = "x";             string n2 = dynamicClass["NameX"] as string;             Console.WriteLine("dynamicClass["NameX"] = '" + n2 + "'");              //GroupByAndSelect_TestDynamicSelectMember();             //Select();             //TestDyn();             //ExpressionTests_Enum();             //Where();             //ExpressionTests_Sum();              Console.WriteLine("--end");         }          private static void GroupByAndSelect_TestDynamicSelectMember()         {             var testList = User.GenerateSampleModels(51).Where(u => u.Profile.Age < 23);             var qry = testList.AsQueryable();              var rrrr = qry.GroupBy2(x => new { x.Profile.Age });             var ll = rrrr.ToDynamicList();              var byAgeReturnAllReal = qry.GroupBy(x => new { x.Profile.Age }).ToList();             var r1 = byAgeReturnAllReal[0];              //var byAgeReturnOK = qry.GroupBy("Profile.Age").ToDynamicList();              // -    [0]  {System.Linq.Grouping<<>f__AnonymousType0<int?>, System.Linq.Dynamic.Core.Tests.Helpers.Models.User>}  object {System.Linq.Grouping<<>f__AnonymousType0<int?>, System.Linq.Dynamic.Core.Tests.Helpers.Models.User>}             var byAgeReturnAll = qry.GroupBy("new (Profile.Age)").OrderBy("Key.Age").ToDynamicList();             var q1 = byAgeReturnAll[0];              var k = q1.Key;             int? age = k.Age;              foreach (var x in byAgeReturnAllReal.OrderBy(a => a.Key.Age))             {                 Console.WriteLine($"age={x.Key.Age} : users={x.ToList().Count}");             }              foreach (var x in byAgeReturnAll)             {                 Console.WriteLine($"age={x.Key.Age} : users={x}");             }         }          private static void TestDyn()         {             var user = new User { UserName = "x" };              dynamic userD = user;             string username = userD.UserName;              Console.WriteLine("..." + username);         }          public static void ExpressionTests_Enum()         {             //Arrange             var lst = new List<TestEnum> { TestEnum.Var1, TestEnum.Var2, TestEnum.Var3, TestEnum.Var4, TestEnum.Var5, TestEnum.Var6 };             var qry = lst.AsQueryable();              //Act             var result1 = qry.Where("it < TestEnum.Var4");             var result2 = qry.Where("TestEnum.Var4 > it");             var result3 = qry.Where("it = Var5");             var result4 = qry.Where("it = @0", TestEnum.Var5);             var result5 = qry.Where("it = @0", 8);              //Assert             int idx = 0;             var ar1 = result1.ToArray();             foreach (var c in new[] { TestEnum.Var1, TestEnum.Var2, TestEnum.Var3 })             {                 Console.Write("*");                 Write((int)c, (int)ar1[idx]);                 idx++;             }              idx = 0;             ar1 = result2.ToArray();             foreach (var c in new[] { TestEnum.Var1, TestEnum.Var2, TestEnum.Var3 })             {                 Console.Write("*");                 Write((int)c, (int)ar1[idx]);                 idx++;             }              Write((int)TestEnum.Var5, (int)result3.Single());             Write((int)TestEnum.Var5, (int)result4.Single());             Write((int)TestEnum.Var5, (int)result5.Single());         }          public static void Where()         {             //Arrange             var testList = User.GenerateSampleModels(100, allowNullableProfiles: true);             var qry = testList.AsQueryable();               //Act             //var xxx = DynamicQueryable             var userById = qry.Where("Id=@0", testList[10].Id);             var userByUserName = qry.Where("UserName="User5"");             var nullProfileCount = qry.Where("Profile=null");             var userByFirstName = qry.Where("Profile!=null && Profile.FirstName=@0", testList[1].Profile.FirstName);               //Assert             Write(testList[10], userById.Single());             Write(testList[5], userByUserName.Single());             Write(testList.Count(x => x.Profile == null), nullProfileCount.Count());             Write(testList[1], userByFirstName.Single());         }          public static void ExpressionTests_Sum()         {             //Arrange             int[] initValues = { 1, 2, 3, 4, 5 };             var qry = initValues.AsQueryable().Select(x => new { strValue = "str", intValue = x }).GroupBy(x => x.strValue);              //Act             var result = qry.Select("Sum(intValue)").AsEnumerable().ToArray()[0];              //Assert             Write(15, result);         }          public static void Select()         {             //Arrange             List<int> range = new List<int> { 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 };             var testList = User.GenerateSampleModels(100);             var qry = testList.AsQueryable();              //Act             IEnumerable rangeResult = range.AsQueryable().Select("it * it");             var userNames = qry.Select("UserName");             var userFirstName = qry.Select("new (UserName, Profile.FirstName as MyFirstName)");             var userRoles = qry.Select("new (UserName, Roles.Select(Id) AS RoleIds)");               //Assert             WriteArray(range.Select(x => x * x).ToArray(), rangeResult.Cast<int>().ToArray());             WriteArray(testList.Select(x => x.UserName).ToArray(), userNames.ToDynamicArray());             WriteArray(testList.Select(x => "{UserName=" + x.UserName + ", MyFirstName=" + x.Profile.FirstName + "}").ToArray(), userFirstName.AsEnumerable().Select(x => x.ToString()).ToArray());              Guid[] check = testList[0].Roles.Select(x => x.Id).ToArray();             //dynamic f = userRoles.First();             //Guid[] ids = f.RoleIds.ToArray();              var userRole = userRoles.First();             Console.WriteLine(">>>>>>>>>>>>>>>>>>" + userRole.ToString());              PropertyInfo[] props = userRole.GetType().GetProperties(BindingFlags.Instance | BindingFlags.Public);             Console.WriteLine(">>>>>>>>>>>>>>>>>> GetProperties = {0}", string.Join(", ", props.Select(p => p.Name)));             Console.WriteLine(">>>>>>>>>>>>>>>>>> GetPropertyValues = {0}", string.Join(", ", props.Select(p => p.GetValue(userRole, null))));              string name = userRole.UserName;              Guid[] result = Enumerable.ToArray(userRole.RoleIds ?? new object[0]);              WriteArray(check, result);         }          private static void Write<T>(T check, T result) where T : class {             Console.WriteLine("> '{0}'", check == result);         }          private static void Write(int check, int result)         {             Console.WriteLine("> {0} == {1} = '{2}'", check, result, check == result);         }          private static void WriteArray<T>(T[] check, T[] result) where T : class {             for (int i = 0; i < check.Length; i++)             {                 Console.WriteLine("> {0} : c={1}, r={2}  '{3}'", i, check[i], result[i], check[i] == result[i]);             }         }          private static void WriteArray(Guid[] check, Guid[] result)         {             for (int i = 0; i < check.Length; i++)             {                 Console.WriteLine("> {0} : c={1}, r={2}  '{3}'", i, check[i], result[i], check[i] == result[i]);             }         }          private static void WriteArray(int[] check, int[] result)         {             for (int i = 0; i < check.Length; i++)             {                 Console.WriteLine("> {0} : c={1}, r={2}  '{3}'", i, check[i], result[i], check[i] == result[i]);             }         }     } } 

  

 

开源地址:

https://github.com/zzzprojects/System.Linq.Dynamic.Core

https://www.nuget.org/packages/System.Linq.Dynamic.Core

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