.net - 无需使用多个 IFS 即可搜索我的网站

Question

我想在我的数据库中搜索表中的产品(产品)问题是我不想要 600 行带有多个 if 的代码。代码如下 atm(不要这样)

Public Function GetSearchResults(ByVal County As Integer, Optional ByVal Searchtext As String = "", Optional ByVal Category As Integer = 0, Optional ByVal SubCategory As Integer = 0) As List(Of Product)
    Dim dc As New DataClassesDataContext
    Dim Listholder As New List(Of Product)

    If Searchtext IsNot "" Then
        If County > 0 Then
            If Category > 0 Then
                If SubCategory = 0 Then
                        Dim Results = From p In dc.Products _
                        Where p.Headline.Contains(Searchtext) _
                        Where p.CategoryID = Category _
                        Where p.CountyID = County _
                        Select p

                        Listholder = Results.ToList
                        Return Listholder.ToList

还有很多 elseifs 等等...问题是，如果上述任何一项的值为 0，则搜索将针对所有县/类别/标题....是否有更好的方法来执行此操作？我的意思是 linq 很棒，必须有办法让它更动态，所以我不需要 IFS。

Answer 1

您可以链接您的 Where 过滤器。

public static void Search(String headline = null, Int32 county = 0, Int32 category = 0, Int32 subCategory = 0) {
    var dc = new DataClassesDataContext();
    var result = dc.Products;

    if (headline != null)
        result = result.Where(p => p.Headline.Contains(headline));

    if (county != 0)
        result = result.Where(p => p.CountyId == county);

    if (category != 0)
        result = result.Where(p => p.CategoryId == category);

    if (subCategory != 0)
        result = result.Where(p => p.SubCategoryId == subCategory);

    var listHolder = result.ToList();
    // ...
}