PredicateBuilder +加入+ VB.NET

Question

我有一個包含3個表

分貝

Products Table   Suppliers Table   Categories Table 
Id      Id       Id 
ProductName    SupplierName    CategoryName 
Quantity    .       . 
SupplierId    .       . 
CategoryId 
. 
.

我使用PredicateBuilder選擇產品accoring到所選擇的產品領域（數量，產品名稱......） 我如何據其Suppliername或類別名稱

使用PredicateBuilder或任何其他方法來選擇產品

請我使用VB.NET我看到了許多C＃的例子，但我不明白，也沒有把它翻譯 我想用加入predicateBuilder的但我不怎麼樣！

爲了更清楚我想要的是多個領域的一個搜索相結合，例如像：

給我看它的名字中包含「s」和數量< 10個產品和SupplierName是奇摩

給我一個我的名字中含有「G」只

給我的產品類別名稱「機」

產品。

。

而這種搜索謂詞是多變的，因爲每一個產品表有很多領域，所以要根據所選字段

等待你的幫助搜索是動態的。

我認爲Arion的答案是正確的，但它需要一些修訂 AnyWay我想出了這個解決方案，它不是最有效的一個，但它解決了我的問題。

Dim SupplierAlso As String = "" 
Dim CategoryAlso As String = "" 
Dim pred = PredicateBuilder.True(Of Products)() 
Select Case Entry 
         Case "Number" 
          Dim Inum = Entry 
          pred = pred.And(Function(m As products) m.ID.Equals(CInt(Inum))) 

         Case "ProductName" 

          Dim IName = Entry 
          pred = pred.And(Function(m As Products) m.ProductName.IndexOf(IName, StringComparison.OrdinalIgnoreCase) >= 0) 

。 。 。 案 「供應商」

      SupplierAlso = Entry 

         Case "Category" 

          CategoryAlso = Ent 

下一頁

  Dim f As ProductsDataTable = Products.Product 
      Dim tmp As IEnumerable(Of Products) = New ProductsDataTable().AsEnumerable() 
      tmp = f.AsEnumerable.Where(pred.Compile) 


      Dim qry 

      If CategoryAlso = "" And SupplierAlso = "" Then 
       q = (From prods In tmp 
         Join Cats In Categories 
         On prods.CategoryId Equals Cats.ID 
         Join Supps In Suppliers 
         On Supps.ID Equals prods.SupplierId 
         Select Supps.SupplierName, Cats.CategoryName, prods.ID _ 
         , prods.ProductName, prods.UnitPrice, prods.CategoryId _ 
         , prods.SupplierId, prods.Location, _ 
         prods.Description, prods.SellPrice, prods.CountInStock _ 
         , prods.ProductionDate, prods.ExpiryDate, _ 
         prods.ProductType, prods.ProductSeason).ToList 

      ElseIf CategoryAlso <> "" And SupplierAlso <> "" Then 

       q = (From prods In tmp 
         Join Cats In Categories 
         On prods.CategoryId Equals Cats.ID 
         Join Supps In Suppliers 
         On Supps.ID Equals prods.SupplierId 
         Where Cats.CategoryName.IndexOf((CategoryAlso) 
       , StringComparison.OrdinalIgnoreCase) >= 0 And _        Supps.SupplierName.IndexOf((SupplierAlso), _ 
         StringComparison.OrdinalIgnoreCase) >= 0 
         Select Supps.SupplierName, Cats.CategoryName, prods.ID, _ 
        prods.ProductName, prods.UnitPrice, prods.CategoryId, _ 
        prods.SupplierId, prods.Location, _ 
         prods.Description, prods.SellPrice, prods.CountInStock, _ 
         prods.ProductionDate, prods.ExpiryDate, _ 
         prods.ProductType, prods.ProductSeason).ToList 

      ElseIf SupplierAlso <> "" And CategoryAlso = "" Then 

       q = (From prods In tmp 
         Join Cats In Categories 
         On Cats.ID Equals prods.CategoryId 
         Join Supps In Suppliers 
         On prods.SupplierId Equals Supps.ID Where _ 
         Supps.SupplierName.IndexOf((SupplierAlso), _ 
         StringComparison.OrdinalIgnoreCase) >= 0 
         Select Cats.CategoryName, Supps.SupplierName, prods.ID, _ 
         prods.ProductName, prods.UnitPrice, prods.CategoryId, _ 
         prods.SupplierId, prods.Location, _ 
         prods.Description, prods.SellPrice, prods.CountInStock, _ 
         prods.ProductionDate, prods.ExpiryDate, _ 
         prods.ProductType, prods.ProductSeason).ToList 

      ElseIf CategoryAlso <> "" And SupplierAlso = "" Then 

       q = (From prods In tmp 
         Join Cats In Categories 
         On prods.CategoryId Equals Cats.ID Where Cats.CategoryName.IndexOf _ 
         ((CategoryAlso), StringComparison.OrdinalIgnoreCase) >= 0 
         Join Supps In Suppliers On Supps.ID Equals prods.SupplierId 
         Select Supps.SupplierName, Cats.CategoryName, prods.ID, _ 
         prods.ProductName, prods.UnitPrice, prods.CategoryId, _ 
         prods.SupplierId, prods.Location, _ 
         prods.Description, prods.SellPrice, prods.CountInStock, _ 
         prods.ProductionDate, prods.ExpiryDate, _ 
         prods.ProductType, prods.ProductSeason).ToList 

      End If 

對於每個IT期q 有了它

    DataGridView2.Rows.Add _ 
        ({.ID, .ProductName, .UnitPrice, .categoryname, .suppliername, .Location, _ 
              .Description, .SellPrice, .CountInStock, _            .ProductionDate, .ExpiryDate, _ 
              .ProductType, .ProductSeason}) 

       End With 

      Next 

那麼你覺得什麼，有沒有更好的辦法？當然是嗎？愚蠢的問題，但在哪裏？

Answer 1

所以我會做這樣的事情。我簡化了where語句，但我認爲你會明白我的觀點：

dim checkCategoryName as boolean=true 
dim checkSupplier as boolean=true 
dim checkQuantity as boolean=true 
dim query= db.Products.Select (function(p) p) 
if checkCategoryName then 
    query=query _ 
      .Where (function(p) db.Categories.Where (function(c) c.CategoryName="??") _ 
      .Select (function(c) c.Id) _ 
      .Contains(p.CategoryId)) 
end if 
if checkSupplier then 
    query=query _ 
      .Where (function(q) db.Suppliers.Where (function(s) s.SupplierName="??") _ 
      .Select (function(s) s.Id) _ 
      .Contains(q.SupplierId)) 
end if 
if checkQuantity then 
    query=query.Where (function(q) q.Quantity<10) 
end if 
dim result=query.ToList() 

其中db是linq數據上下文。