要创建动态LINQ连接扩展方法,您需要遵循以下步骤:
Install-Package System.Linq.Dynamic.Core
using System.Linq.Dynamic.Core;
public static IQueryable<T> DynamicJoin<T>(this IQueryable<T> source, string joinCondition)
{
// 实现动态连接逻辑
}
Queryable.Join
方法创建连接查询:public static IQueryable<T> DynamicJoin<T>(this IQueryable<T> source, string joinCondition)
{
var sourceType = typeof(T);
var sourceProperties = sourceType.GetProperties();
var joinConditionParts = joinCondition.Split('=');
var sourceKey = joinConditionParts[0];
var targetKey = joinConditionParts[1];
var targetType = sourceProperties.First(p => p.Name == sourceKey).PropertyType;
var targetProperties = targetType.GetProperties();
var targetTable = targetProperties.First(p => p.Name == targetKey).GetValue(null);
var sourceParam = Expression.Parameter(sourceType, "s");
var targetParam = Expression.Parameter(targetType, "t");
var sourceKeySelector = Expression.Lambda(Expression.Property(sourceParam, sourceKey), sourceParam);
var targetKeySelector = Expression.Lambda(Expression.Property(targetParam, targetKey), targetParam);
var resultSelector = Expression.Lambda(
Expression.MemberInit(
Expression.New(typeof(T)),
Expression.Bind(sourceType.GetProperty(sourceKey), targetParam)
),
sourceParam,
targetParam
);
var joinMethod = typeof(Queryable)
.GetMethods()
.First(m => m.Name == "Join" && m.GetParameters().Length == 5)
.MakeGenericMethod(sourceType, targetType, sourceKeySelector.ReturnType, resultSelector.ReturnType);
return joinMethod.Invoke(null, new object[] { source, targetTable, sourceKeySelector, targetKeySelector, resultSelector }) as IQueryable<T>;
}
DynamicJoin
扩展方法动态连接任何IQueryable实例。例如:var source = new[] { new { Id = 1, Name = "John" } }.AsQueryable();
var target = new[] { new { Id = 1, Age = 30 } }.AsQueryable();
var result = source.DynamicJoin("Id = Id");
这将创建一个连接查询,其中源和目标实例根据它们的Id属性进行连接。结果将包含一个匿名类型,该类型具有源实例的所有属性以及目标实例的所有属性。
请注意,这只是一个简单的示例,您可能需要根据您的具体需求对其进行调整。
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