linq下 多条件 on后面多条件 左连接

linq下 多条件  on后面多条件  

1、左连接的实现主要是基于  join 后加 into   变量1
from 变量 in 变量1.DefaultIfEmpty()

2、这里还有一个多条件的例子：

new{ColorCode=productColor.ColorCode,PTCode="ProductColors" } equals new {ColorCode=parameter.PValue,PTCode=parameter.PTCode} 
匿名类里放多个值equals 来实现多条件联合查询

       下面是多个表联合左查询 多条件实例

        var queryMatial = from palnOrder in _substationPlanOrderItemRepository.Entities                              join productInfo in _productInfoRepository.Entities on palnOrder.ProductCode equals productInfo.ProductCode into left1                              from productInfo in left1.DefaultIfEmpty()                              join brandInfo in _brandInfoRepository.Entities on productInfo.BrandCode equals brandInfo.BrandCode into left2                              from brandInfo in left2.DefaultIfEmpty()                              join productColor in _productColorRepository.Entities on productInfo.ProductCode equals productColor.ProductCode into left3                              from productColor in left3.DefaultIfEmpty()                              join parameter in _parameterRepository.Entities on new{ColorCode=productColor.ColorCode,PTCode="ProductColors" } equals new {ColorCode=parameter.PValue,PTCode=parameter.PTCode}  into left4                              from parameter in left4.DefaultIfEmpty()                              join productCata in _productCategoryRepository.Entities on productInfo.CategoryCodeMain equals productCata.CategoryCode into left5                              from productCata in left5.DefaultIfEmpty()                             // where parameter.PTCode == "ProductColors"                              select new orderMatialEntity                              {                                  ProductId = productInfo.ProductId,                                  ProductCode = productInfo.ProductCode,                                  ProductName = productInfo.ProductName,                                  BrandCode = productInfo.BrandCode,                                  BrandName = brandInfo.BrandName,                                  Model = productInfo.Model,                                  Specifications = productInfo.Specifications,                                  Material = productInfo.Material,                                  Color = parameter.PValue,                                  Qnty = palnOrder.Qnty.Value,                                  Remark = palnOrder.Remark,                                  ProductStatus = palnOrder.ProductStatus,                                  PurchaseCode = palnOrder.PurchaseCode,                                  MainCatalogCode = productCata.CategoryCode,                                  MainCatalogName = productCata.CategoryName                              };

自己记录下 请大神指导优化或者同行斧正！