选择内连接左表到实体框架拦截器中的DbScanExpression [英] Selecting Left Table on Inner Join to DbScanExpression in Entity Framework Interceptor

问题描述

在这个问题上，回答这里 ，我试图选择正确表中的所有列，而不必从左侧表格中明确指定列名与UserId。

Further to the SO question answered here, i'm trying to select all of the columns in the right table only without having to explicitly specify the column names together with UserId from the left table.

任何想法如何做到这一点？

Any ideas on how this can be done?

public override DbExpression Visit(DbScanExpression expression)
{
    var table = expression.Target.ElementType as EntityType;
    if (table != null && table.Name == "User")
    {
        return expression.InnerJoin(
            DbExpressionBuilder.Scan(expression.Target.EntityContainer.BaseEntitySets.Single(s => s.Name == "TennantUser")),
            (l, r) =>
                DbExpressionBuilder.Equal(
                    DbExpressionBuilder.Property(l, "UserId"),
                    DbExpressionBuilder.Property(r, "UserId")
                )
        )
        .Select(exp => 
            new { 
                UserId = exp.Property("l").Property("UserId"), 
                Email = exp.Property("l").Property("Email") 
            });
    }

    return base.Visit(expression);
}

推荐答案

也许答案有点迟了，但无论如何可能会帮助某人节省时间

Maybe the answer is a bit late, but anyway it may help a someone to save a time

 public override DbExpression Visit(DbScanExpression expression)
    {
        var table = expression.Target.ElementType as EntityType;

        if (table != null && table.Name == "User")
        {
            var rightExpression = expression.Target.EntityContainer.GetEntitySetByName("TennantUser", true).Scan();

            var join = expression.InnerJoin(rightExpression,
                (l, r) =>
                        DbExpressionBuilder.Equal(
                            DbExpressionBuilder.Property(l, "UserId"),
                            DbExpressionBuilder.Property(r, "UserId")
                        ));


            var select = join.Select(exp => DbExpressionBuilder.NewRow(
                expression.Target.ElementType.Members.Select(x => 
                    new KeyValuePair<string, DbExpression>(x.Name, exp.Property(join.Left.VariableName).Property(x.Name)))));


            return select;

        }

        return base.Visit(expression);
    }

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