實體框架代碼第一個動態查詢

Question

這段代碼很糟糕，我只搜索一個屬性（CompanyName）。我該如何動態地編寫這個查詢，或者在任何情況下都更好？

public List<SubContractor> GetSearchSubcontractorList() 
    { 
     var list = CacheObjects.Subcontractors; 
     var searchItem = string.Empty; 
     if (string.IsNullOrWhiteSpace(this.SearchCompanyName) == false) 
     { 
      var indexes = this.SearchCompanyName.IndexOfAll("*").ToList(); 
      if (indexes.Any() == false) 
      { 
       list = list.Where(x => x.CompanyName == this.SearchCompanyName).ToList(); 
      } 

      if (indexes.Count() == 1) 
      { 
       if (this.SearchCompanyName.StartsWith("*")) 
       { 
        searchItem = this.SearchCompanyName.Replace("*", string.Empty); 
        list = list.Where(x => x.CompanyName.EndsWith(searchItem)).ToList(); 
       } 
       else 
       { 
        searchItem = this.SearchCompanyName.Replace("*", string.Empty); 
        list = list.Where(x => x.CompanyName.StartsWith(searchItem)).ToList(); 
       } 
      } 

      if (indexes.Count() == 2) 
      { 
       searchItem = this.SearchCompanyName.Replace("*", string.Empty); 
       list = list.Where(x => x.CompanyName.Contains(searchItem)).ToList(); 
      } 
     } 

     return list; 
    } 

Answer 1

對不起，我錯了。我編輯過，檢查出新的解決方案。我認爲你只有4種不同的情況可以測試嗎？沒有通配符，以通配符開頭，以通配符結尾，通配符結束。新的解決方案使用延遲的查詢執行，以便您可以繼續使用更多屬性構建查詢。公正的警告，仍然沒有遵守...

var filteredSubcontractors = (from s in list 
          select s); 

    if (string.IsNullOrWhiteSpace(this.SearchCompanyName) == false) 
    { 
     searchItem = this.SearchCompanyName.Replace("*", string.Empty); 

     if (!SearchCompanyName.Contains("*")) 
     { 
      filteredSubcontractors = (from s in filteredSubcontractors 
          where s.CompanyName == this.SearchCompanyName 
          select s); 
     } 
     else if(SearchCompanyName.StartsWith("*")) 
     {  
      filteredSubcontractors = (from s in filteredSubcontractors 
          where s.CompanyName.EndsWith(searchItem) 
          select s); 
     } 
     else if(SearchCompanyName.EndsWith("*")) 
     { 
      filteredSubcontractors = (from s in filteredSubcontractors 
          where s.CompanyName.StartsWith(searchItem) 
          select s); 
     } 
     else 
     { 
      filteredSubcontractors = (from s in filteredSubcontractors 
          where s.CompanyName.Contains(searchItem) 
          select s); 
     } 
    } 

    ... 
    //Repeat for as many other properties that you want to filter on 
    ... 

    //All the conditions that you added will not actually be evaluated 
    //until this line is executed. 
    var result = filteredSubcontractors.ToList(); 

    return result; 

你也可以看看這個堆棧溢出問題。在這裏有很多其他的想法（可能比我更好）。 Generating LinqToEntities Where statement depending on the user selection