如何创建动态LINQ连接扩展方法

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
}

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>;
}

var source = new[] { new { Id = 1, Name = "John" } }.AsQueryable();
var target = new[] { new { Id = 1, Age = 30 } }.AsQueryable();

var result = source.DynamicJoin("Id = Id");