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I am trying to learn Entity Framework. I am happy that the results I am returning from my queries are giving me the data that I need but I find that I am using allot of for-each loops and separate database requests to get the information I require.

I would be grateful if someone could review my code and advise if there is a way I could make things more concise and also if I am not really getting the functionality that the entity framework offers ( I think I am missing the point here somewhere!!!). Any way here is the problem and the code (which I hope makes sense):

Attempting to query from 4 tables in my database. One is unrelated (due to my laziness - I need to amend this but it is not a deal breaker at present). The other 3 are related with a 1 to many relationship. here is a summary:

UserClients - unrelated table (should be linked to LeadClient but not important)

[LeadClient PK = GroupCode] one to may to [Matters FK = LeadCode] [Matters PK = MatterNumber] one to many to [Invoices FK = Matter]

I am attempting to create a list of DTO objects to populate a GridView. My DTO is as follows:

public class dto
{
    public string clientCode { get; set; }
    public string clientName { get; set; }
    public decimal totalDebt { get; set; }


}

I am passing in a statementName variable to a method which I then query against UserClients to get a List of clientcodes.

Here is my method to populate my List objects:

      public static List<dto> StateNameLeadCodes(string stateName)
    {
        //DTO objects
        List<dto> items = new List<dto>();

        //Leadcode list for statement name
        List<string> leadcodes = (from o in repository.UserClients where o.StatementName == stateName select o.LeadCode).ToList();

        //From leadcodes populate items list
       foreach(string s in leadcodes)
       {
           //Get clientCode and matter list for the client code
           var code = (from o in repository.LeadClients where o.GroupCode == s select new { o.ClientName, o.Matters}).First();


           dto temp = new dto();

           temp.clientCode = s;

           temp.clientName = code.ClientName;


           //Get a list if invoices for each matter 
           foreach (Matter m in code.Matters)
           {
               List<Invoice> invoices = (from o in repository.Invoices where o.Matter == m.Matternumber select o).ToList();
               //Calculate total debt for all invoices
               foreach (Invoice inv in invoices)
               {
                   temp.totalDebt += (inv.debt_Fee + inv.debt_Costs + inv.debt_VAT);
               }

           }

                items.Add(temp);
            }


        return items;
         }

I find myself doing something similar when I want to return a combination of a single item and a list to a DTO. I see that my Entity classes have an EntityCollection for the One to Many relationship. I have tried to select the entity object as part of my select statements but I get the error that the EnitityCollection cannot be converted to a List<>.

Any tips and pointers how to clean this code up would be great - thanks in advance!!

Added image of Entity objects as requested:

EntityImage

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1 に答える 1

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私がすべてを正しく読んで理解したかどうかはわかりませんが（私にとっては本当に読むのが難しいです:)）、この解決策を試すことができます：

public static List<dto> StateNameLeadCodes(string stateName)
{
    return (from uc in repository.UserClients
            join lc in repository.LeadClients
                on uc.LeadCode equals lc.GroupCode
            where uc.StatementName == stateName
            select new dto
            {
                clientCode = uc.LeadCode,
                clientName = lc.ClientName,
                totalDebt = lc.Matters
                    .Sum(m => m.Invoices
                        .Sum(i => i.debt_Fee + i.debt_Costs + i.debt_VAT))
            }).ToList();
}

LeadClientのMatterコレクションまたはMatterのInvoicesコレクションが空の場合、EFは空のコレクションの合計を値に具体化できないため、問題が発生する可能性がありdecimalます。次のようなものを使用する必要があるかもしれません

totalDebt = lc.Matters
    .Sum(m => m.Invoices
        .Sum(i => (decimal?)(i.debt_Fee + i.debt_Costs + i.debt_VAT)) ?? 0m)
于 2012-10-08T22:38:43.860 に答える