DbContext.SaveChanges

Question

我有一個問題，即向實體ProfessionalEmploymentRecord EF插入一條記錄，最終分別在每個實體中複製現有的Professional，Program，Role記錄。我曾嘗試在數據庫中明確初始化Professional，Program，Role和現有的鍵/值對，但EF仍然使用新鍵創建重複值。

public class ProfessionalEmploymentRecord 
{ 
    public int ProfessionalEmploymentRecordId {get; set; } 

    public virtual Professional Professional { get; set; } 
    public virtual Program Program { get; set; } 
    public virtual Role Role { get; set; } 
} 
public class Program 
{ 
    public int ProgramId { get; set; } 
    [MaxLength(20)] 
    public string Name { get; set; } 
} 
public class Role 
{ 
    public int RoleId { get; set; } 
    [MaxLength(50)] 
    public string Name { get; set; } 
} 
public class Professional 
{ 
    public int ProfessionalId { get; set; } 
    [MaxLength(20)] 
    public string Name { get; set; } 
} 

當使用下面的Create時，我最終得到三個相關實體中的新記錄，雖然它們存在並有一個鍵集。換句話說，我最終得到三個相關實體中具有新主鍵的值副本（增加1）。

public ActionResult Create(ProfessionalEmploymentRecord professionalemploymentrecord) 
    { 
     if (ModelState.IsValid) 
     { 
      db.ProfessionalEmploymentRecords.Add(professionalemploymentrecord); 
      db.SaveChanges(); 
      return RedirectToAction("Index"); 
     } 
     return View(professionalemploymentrecord); 
    } 

按照要求

我已經使用以下代碼來測試

@model My.Models.ProfessionalEmploymentRecord 
@{ 
ViewBag.Title = "Create"; 
} 
<h2>Create</h2> 
@using (Html.BeginForm()) { 
@Html.ValidationSummary(true) 
<fieldset> 
    <legend> Professional Employment Record</legend> 

    <div class="editor-label"> 
     Professional 
    </div> 
    <div class="editor-field"> 
     @Html.EditorFor(model => model.Professional.Name) 
     @Html.ValidationMessageFor(model => model.Professional.Name) 
    </div> 
    <div class="editor-label"> 
     Program 
    </div> 
    <div class="editor-field"> 
     @Html.EditorFor(model => model.Program.Name) 
     @Html.ValidationMessageFor(model => model.Program.Name) 
    </div> 
    <div class="editor-label"> 
     Role 
    </div> 
    <div class="editor-field"> 
     @Html.EditorFor(model => model.Role.Name) 
     @Html.ValidationMessageFor(model => model.Role.Name) 
    </div> 
    <p> 
     <input type="submit" value="Create" /> 
    </p> 
</fieldset> 
} 

<div> 
@Html.ActionLink("Back to List", "Index") 
</div> 

。 （我看到執行SaveChanges設置* Id ++在記錄）。

public void TestDummyAdd() 
    { 
     Professional prof = new Professional { ProfessionalId = 1, Name = "Chris" }; 
     Program prog = new Program { ProgramId = 1, Name = "A" }; 
     Role role = new Role { RoleId = 1, Name = "B" }; 
     ProfessionalEmploymentRecord reco = new ProfessionalEmploymentRecord { Professional = prof, Role = role, Program = prog, ProfessionalEmploymentRecordId = 0 }; 

     if (ModelState.IsValid) 
     { 
      db.ProfessionalEmploymentRecords.Add(reco); 
      db.SaveChanges(); 
     } 
    } 

Answer 1

添加是在整個對象圖上執行的操作。如果添加記錄，則還要添加其所有關係，它們的關係等。有兩個選項可以解決此問題，並且都需要您手動設置持久對象grap中某些實體的狀態（有時也包含關係）：

• 呼叫Add像你一樣，但在那之後，你必須在圖形要麼Unchanged或Modified所有現有實體（實體將在數據庫中udpated）
• 呼叫Attach，而不是Add設置狀態和集後所有新實體的狀態爲Added

個

設置狀態可以這樣做：

db.Entry(entity).State = EntityState.Added;