LINQ中的动态连接0 C# [英] dynamic join in linq 0 c#

问题描述

   var query = from C in db.clients
    join O in db.orders on c.clientid equals O.clientid
    join P in db.products on O.productid equals P.productid
    select new {C,O};

我想基于上述联接进行搜索.输入参数可以是

I want to perform a search based on the above join. The input param could be

C.ClientID和/或P.ProductName和/或P.ProductType和/或O.ShippingType

C.ClientID and/or P.ProductName and/or P.ProductType and/or O.ShippingType

我将如何构建动态搜索子句?

How would i build a dynamic search clause?

推荐答案

另一种方法:

Expression<Func<Client, bool>> clientWhere = c => true;
Expression<Func<Order, bool>> orderWhere = o => true;
Expression<Func<Product, bool>> productWhere = p => true;

if (filterByClient)
{
    clientWhere = c => c.ClientID == searchForClientID;
}

if (filterByProductName)
{
    productName = p => p.ProductName == searchForProductNameString;
}

// other filter cases

var query = from C in db.clients.Where(clientWhere)
    join O in db.orders.Where(orderWhere) on c.clientid equals O.clientid
    join P in db.products.Where(productWhere) on O.productid equals P.productid
    select new {C,O};

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