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當我嘗試使用LINQ to SQL插入新記錄 時，我遇到了一個非常令人沮喪的問題。如果我單步執行此代碼，有時會插入新記錄 ，但大多數情況下不會。當它失敗時，我看到以下錯誤。LINQ to SQL INSERT失敗
無法插入NULL值插入 列 '名稱'，表 'EquipmentManufacturer';列確實是 不允許有空值。 INSERT失敗。 聲明已被終止。
這個錯誤是抱怨'姓名'字段爲空，但不應該是這種情況。當我調試並逐步完成這個集合時[[Name]]具有我在表單中輸入的值。
這是表格創建語句。
CREATE TABLE [EquipmentManufacturer] (
[EquipmentManufacturerID] [int] IDENTITY(1,1) NOT NULL,
[Name] [nvarchar](50) NOT NULL,
CONSTRAINT [PK_EquipmentManufacturer] PRIMARY KEY CLUSTERED
(
[EquipmentManufacturerID] ASC
) ON [PRIMARY]
) ON [PRIMARY]
這裏是ASP.NET MVC控制器和創建操作，我試圖添加一條新記錄。
public partial class EquipmentManufacturerController : Controller
{
private IRepository<EquipmentManufacturer> reposManu;
// POST: /EquipmentManufacturer/Create
[AcceptVerbs(HttpVerbs.Post)]
public virtual ActionResult Create(FormCollection collection)
{
EquipmentManufacturer entity = reposManu.New();
try
{
//HACK: Something screwy is going on here the entity oject doesn't always get updated correctly
//UpdateModel(entity);
entity.Name = collection["Name"];
reposManu.Insert(entity);
reposManu.SubmitChanges();
return RedirectToAction("Details", new { id = entity.EquipmentManufacturerID });
}
catch (RulesException ex)
{
ex.AddModelStateErrors(ModelState, "EquipmentManufacturer");
return ModelState.IsValid ? RedirectToAction("Create")
: (ActionResult)View();
}
}
}
這裏是Create.aspx視圖。
<asp:Content ID="Content2" ContentPlaceHolderID="MainContent" runat="server">
<h2>Create</h2>
<%= Html.ValidationSummary("Create was unsuccessful. Please correct the errors and try again.") %>
<% using (Html.BeginForm()) {%>
<fieldset>
<legend>Fields</legend>
<p>
<label for="Name">Name:</label>
<%= Html.TextBox("Name") %>
<%= Html.ValidationMessage("Name") %>
</p>
<p>
<input type="submit" value="Create" />
</p>
</fieldset>
<% } %>
<%= Html.ClientSideValidation<EquipmentManufacturer>() %>
<div>
<%=Html.ActionLink("Back to List", "Index") %>
</div>
</asp:Content>
這是我正在使用的Repository實現。
public class Repository<T> : IRepository<T> where T : class
{
public IDataContext DC { get; set; }
public Repository(IDataContext dataContext)
{
DC = dataContext;
}
/// <summary>
/// Return all instances of type T.
/// </summary>
/// <returns></returns>
public IEnumerable<T> All()
{
return GetTable;
}
/// <summary>
/// Return all instances of type T that match the expression exp.
/// </summary>
/// <param name="exp"></param>
/// <returns></returns>
public IQueryable<T> Find(Expression<Func<T, bool>> exp)
{
return GetTable.Where<T>(exp);
}
/// <summary>See IRepository</summary>
/// <param name="exp"></param>
/// <returns></returns>
public T Single(Expression<Func<T, bool>> exp)
{
return GetTable.SingleOrDefault(exp);
}
/// <summary>See IRepository</summary>
/// <param name="exp"></param>
/// <returns></returns>
public T First(Expression<Func<T, bool>> exp)
{
return GetTable.First(exp);
}
/// <summary>See IRepository</summary>
/// <param name="entity"></param>
public virtual void Delete(T entity)
{
DC.Context.GetTable<T>().DeleteOnSubmit(entity);
}
/// <summary>
/// Create a new instance of type T.
/// </summary>
/// <returns></returns>
public virtual T New()
{
T entity = Activator.CreateInstance<T>();
GetTable.InsertOnSubmit(entity);
return entity;
}
/// <summary>
/// Adds an insance T.
/// </summary>
/// <returns></returns>
public virtual void Insert(T entity)
{
GetTable.InsertOnSubmit(entity);
}
/// <summary>
/// Update entity.
/// </summary>
/// <returns></returns>
public virtual void Update(T entity)
{
DC.Context.Refresh(System.Data.Linq.RefreshMode.KeepCurrentValues, entity);
}
/// <summary>See IRepository</summary>
public void SubmitChanges()
{
DC.SubmitChanges();
}
private string PrimaryKeyName
{
get { return TableMetadata.RowType.IdentityMembers[0].Name; }
}
private System.Data.Linq.Table<T> GetTable
{
get { return DC.Context.GetTable<T>(); }
}
private System.Data.Linq.Mapping.MetaTable TableMetadata
{
get { return DC.Context.Mapping.GetTable(typeof(T)); }
}
private System.Data.Linq.Mapping.MetaType ClassMetadata
{
get { return DC.Context.Mapping.GetMetaType(typeof(T)); }
}
}
這似乎解決了我的問題，但我不太確定爲什麼。如果我從Repository New方法註釋掉GetTable.InsertOnSubmit（實體），它會起作用。如果我在Repository New方法中留下InsertOnSubmit調用，並在控制器中註釋掉reposManu.Insert（entity）調用，它將失敗。 – MHinton 2009-08-26 13:12:57
根據你剛纔所說的判斷，當你調用.InsertOnSubmit（entity）時，它需要一個對象的副本來保存它。因此，當你打電話給.InsertOnSubmit打上新的EquipmentManufacturer品牌時，它會嘗試插入一個不包含任何值的副本，因此它會因數據庫限制而失敗。 – Charlino 2009-08-26 19:49:46
謝謝，這實際上是有道理的。 – MHinton 2009-08-27 00:48:57