c# - db.savechanges() 不工作

Question

我正在学习本教程 Creating Master-Details Windows Forms with the Entity Framework但是如果我修改了某些列或添加了新行，db.Savechanges() 将不起作用。根据这个视频教程，它会起作用，但它不起作用。

Product_Form.cs

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows.Forms;

namespace RemoteSynchronizer
{
    public partial class Product : Form
    {

        ProductsEntities db = new ProductsEntities();
        public Product()
        {
            InitializeComponent();
        }

        private void Product_Form_Load(object sender, EventArgs e)
        {
            product_DBindingSource.DataSource = db.Product_D.ToList();
        }

        private void bindingNavigatorAddNewItem_Click(object sender, EventArgs e)
        {

        }

        private void product_DBindingNavigatorSaveItem_Click(object sender, EventArgs e)
        {
            // Product_D obj = new Product_D();
            // obj.PCode = pCodeTextBox.Text;
            // obj.Name = nameTextBox.Text;
            // obj.Batch = batchTextBox.Text;
            // obj.Expiry = expiryTextBox.Text;
            // obj.Price = priceTextBox.Text;

            //try
            // {
            //     Product_D temp = db.Product_D.Single(t => t.PCode == pCodeTextBox.Text);

            //     MessageBox.Show("Product Exists");
            // }
            // catch 
            // {
            //     db.Product_D.Add(obj);
                 db.SaveChanges();

             //}

        }

        private void bindingNavigatorDeleteItem_Click(object sender, EventArgs e)
        {

        }

    }
}

当我尝试在代码中使用注释方法时出现错误

错误

************** Exception Text **************
System.Data.Entity.Infrastructure.DbUpdateException: Unable to update the EntitySet 'Product_D' because it has a DefiningQuery and no <InsertFunction> element exists in the <ModificationFunctionMapping> element to support the current operation. ---> System.Data.UpdateException: Unable to update the EntitySet 'Product_D' because it has a DefiningQuery and no <InsertFunction> element exists in the <ModificationFunctionMapping> element to support the current operation.
   at System.Data.SqlClient.SqlGen.DmlSqlGenerator.ExpressionTranslator.Visit(DbScanExpression expression)
   at System.Data.Common.CommandTrees.DbScanExpression.Accept(DbExpressionVisitor visitor)
   at System.Data.SqlClient.SqlGen.DmlSqlGenerator.GenerateInsertSql(DbInsertCommandTree tree, SqlVersion sqlVersion, List`1& parameters)
   at System.Data.SqlClient.SqlGen.SqlGenerator.GenerateSql(DbCommandTree tree, SqlVersion sqlVersion, List`1& parameters, CommandType& commandType, HashSet`1& paramsToForceNonUnicode)
   at System.Data.SqlClient.SqlProviderServices.CreateCommand(DbProviderManifest providerManifest, DbCommandTree commandTree)
   at System.Data.SqlClient.SqlProviderServices.CreateCommand(DbCommandTree commandTree)
   at System.Data.Mapping.Update.Internal.UpdateTranslator.CreateCommand(DbModificationCommandTree commandTree)
   at System.Data.Mapping.Update.Internal.DynamicUpdateCommand.CreateCommand(UpdateTranslator translator, Dictionary`2 identifierValues)
   at System.Data.Mapping.Update.Internal.DynamicUpdateCommand.Execute(UpdateTranslator translator, EntityConnection connection, Dictionary`2 identifierValues, List`1 generatedValues)
   at System.Data.Mapping.Update.Internal.UpdateTranslator.Update(IEntityStateManager stateManager, IEntityAdapter adapter)
   at System.Data.EntityClient.EntityAdapter.Update(IEntityStateManager entityCache)
   at System.Data.Objects.ObjectContext.SaveChanges(SaveOptions options)
   at System.Data.Entity.Internal.InternalContext.SaveChanges()
   --- End of inner exception stack trace ---
   at System.Data.Entity.Internal.InternalContext.SaveChanges()
   at System.Data.Entity.Internal.LazyInternalContext.SaveChanges()
   at System.Data.Entity.DbContext.SaveChanges()
   at RemoteSynchronizer.Product.product_DBindingNavigatorSaveItem_Click(Object sender, EventArgs e) in e:\Study\Project\RemoteSynchronizer\RemoteSynchronizer\Product_Form.cs:line 50
   at System.Windows.Forms.ToolStripItem.RaiseEvent(Object key, EventArgs e)
   at System.Windows.Forms.ToolStripButton.OnClick(EventArgs e)
   at System.Windows.Forms.ToolStripItem.HandleClick(EventArgs e)
   at System.Windows.Forms.ToolStripItem.HandleMouseUp(MouseEventArgs e)
   at System.Windows.Forms.ToolStripItem.FireEventInteractive(EventArgs e, ToolStripItemEventType met)
   at System.Windows.Forms.ToolStripItem.FireEvent(EventArgs e, ToolStripItemEventType met)
   at System.Windows.Forms.ToolStrip.OnMouseUp(MouseEventArgs mea)
   at System.Windows.Forms.Control.WmMouseUp(Message& m, MouseButtons button, Int32 clicks)
   at System.Windows.Forms.Control.WndProc(Message& m)
   at System.Windows.Forms.ScrollableControl.WndProc(Message& m)
   at System.Windows.Forms.ToolStrip.WndProc(Message& m)
   at System.Windows.Forms.Control.ControlNativeWindow.OnMessage(Message& m)
   at System.Windows.Forms.Control.ControlNativeWindow.WndProc(Message& m)
   at System.Windows.Forms.NativeWindow.Callback(IntPtr hWnd, Int32 msg, IntPtr wparam, IntPtr lparam)


************** Loaded Assemblies **************
mscorlib
    Assembly Version: 4.0.0.0
    Win32 Version: 4.0.30319.18010 built by: FX45RTMGDR
    CodeBase: file:///C:/Windows/Microsoft.NET/Framework/v4.0.30319/mscorlib.dll
----------------------------------------
RemoteSynchronizer
    Assembly Version: 1.0.0.0
    Win32 Version: 1.0.0.0
    CodeBase: file:///E:/Study/Project/RemoteSynchronizer/RemoteSynchronizer/bin/Debug/RemoteSynchronizer.exe
----------------------------------------
System.Windows.Forms
    Assembly Version: 4.0.0.0
    Win32 Version: 4.0.30319.17929 built by: FX45RTMREL
    CodeBase: file:///C:/Windows/Microsoft.Net/assembly/GAC_MSIL/System.Windows.Forms/v4.0_4.0.0.0__b77a5c561934e089/System.Windows.Forms.dll
----------------------------------------
System.Drawing
    Assembly Version: 4.0.0.0
    Win32 Version: 4.0.30319.17929 built by: FX45RTMREL
    CodeBase: file:///C:/Windows/Microsoft.Net/assembly/GAC_MSIL/System.Drawing/v4.0_4.0.0.0__b03f5f7f11d50a3a/System.Drawing.dll
----------------------------------------
System
    Assembly Version: 4.0.0.0
    Win32 Version: 4.0.30319.18016 built by: FX45RTMGDR
    CodeBase: file:///C:/Windows/Microsoft.Net/assembly/GAC_MSIL/System/v4.0_4.0.0.0__b77a5c561934e089/System.dll
----------------------------------------
System.Configuration
    Assembly Version: 4.0.0.0
    Win32 Version: 4.0.30319.17929 built by: FX45RTMREL
    CodeBase: file:///C:/Windows/Microsoft.Net/assembly/GAC_MSIL/System.Configuration/v4.0_4.0.0.0__b03f5f7f11d50a3a/System.Configuration.dll
----------------------------------------
System.Xml
    Assembly Version: 4.0.0.0
    Win32 Version: 4.0.30319.17929 built by: FX45RTMREL
    CodeBase: file:///C:/Windows/Microsoft.Net/assembly/GAC_MSIL/System.Xml/v4.0_4.0.0.0__b77a5c561934e089/System.Xml.dll
----------------------------------------
System.Web
    Assembly Version: 4.0.0.0
    Win32 Version: 4.0.30319.17929 built by: FX45RTMREL
    CodeBase: file:///C:/Windows/Microsoft.Net/assembly/GAC_32/System.Web/v4.0_4.0.0.0__b03f5f7f11d50a3a/System.Web.dll
----------------------------------------
System.Core
    Assembly Version: 4.0.0.0
    Win32 Version: 4.0.30319.17929 built by: FX45RTMREL
    CodeBase: file:///C:/Windows/Microsoft.Net/assembly/GAC_MSIL/System.Core/v4.0_4.0.0.0__b77a5c561934e089/System.Core.dll
----------------------------------------
EntityFramework
    Assembly Version: 5.0.0.0
    Win32 Version: 5.0.20627.0
    CodeBase: file:///E:/Study/Project/RemoteSynchronizer/RemoteSynchronizer/bin/Debug/EntityFramework.DLL
----------------------------------------
System.Data.Entity
    Assembly Version: 4.0.0.0
    Win32 Version: 4.0.30319.17929 built by: FX45RTMREL
    CodeBase: file:///C:/Windows/Microsoft.Net/assembly/GAC_MSIL/System.Data.Entity/v4.0_4.0.0.0__b77a5c561934e089/System.Data.Entity.dll
----------------------------------------
Anonymously Hosted DynamicMethods Assembly
    Assembly Version: 0.0.0.0
    Win32 Version: 4.0.30319.18010 built by: FX45RTMGDR
    CodeBase: file:///C:/Windows/Microsoft.Net/assembly/GAC_32/mscorlib/v4.0_4.0.0.0__b77a5c561934e089/mscorlib.dll
----------------------------------------
Accessibility
    Assembly Version: 4.0.0.0
    Win32 Version: 4.0.30319.17929 built by: FX45RTMREL
    CodeBase: file:///C:/Windows/Microsoft.Net/assembly/GAC_MSIL/Accessibility/v4.0_4.0.0.0__b03f5f7f11d50a3a/Accessibility.dll
----------------------------------------
System.Data
    Assembly Version: 4.0.0.0
    Win32 Version: 4.0.30319.17929 built by: FX45RTMREL
    CodeBase: file:///C:/Windows/Microsoft.Net/assembly/GAC_32/System.Data/v4.0_4.0.0.0__b77a5c561934e089/System.Data.dll
----------------------------------------
System.Transactions
    Assembly Version: 4.0.0.0
    Win32 Version: 4.0.30319.17929 built by: FX45RTMREL
    CodeBase: file:///C:/Windows/Microsoft.Net/assembly/GAC_32/System.Transactions/v4.0_4.0.0.0__b77a5c561934e089/System.Transactions.dll
----------------------------------------
System.Numerics
    Assembly Version: 4.0.0.0
    Win32 Version: 4.0.30319.17929 built by: FX45RTMREL
    CodeBase: file:///C:/Windows/Microsoft.Net/assembly/GAC_MSIL/System.Numerics/v4.0_4.0.0.0__b77a5c561934e089/System.Numerics.dll
----------------------------------------
System.Data.OracleClient
    Assembly Version: 4.0.0.0
    Win32 Version: 4.0.30319.17929 built by: FX45RTMREL
    CodeBase: file:///C:/Windows/Microsoft.Net/assembly/GAC_32/System.Data.OracleClient/v4.0_4.0.0.0__b77a5c561934e089/System.Data.OracleClient.dll
----------------------------------------
System.Xml.Linq
    Assembly Version: 4.0.0.0
    Win32 Version: 4.0.30319.17929 built by: FX45RTMREL
    CodeBase: file:///C:/Windows/Microsoft.Net/assembly/GAC_MSIL/System.Xml.Linq/v4.0_4.0.0.0__b77a5c561934e089/System.Xml.Linq.dll
----------------------------------------
System.EnterpriseServices
    Assembly Version: 4.0.0.0
    Win32 Version: 4.0.30319.17929 built by: FX45RTMREL
    CodeBase: file:///C:/Windows/Microsoft.Net/assembly/GAC_32/System.EnterpriseServices/v4.0_4.0.0.0__b03f5f7f11d50a3a/System.EnterpriseServices.dll
----------------------------------------
EntityFrameworkDynamicProxies-RemoteSynchronizer
    Assembly Version: 1.0.0.0
    Win32 Version: 4.0.30319.17929 built by: FX45RTMREL
    CodeBase: file:///C:/Windows/Microsoft.Net/assembly/GAC_MSIL/System.Data.Entity/v4.0_4.0.0.0__b77a5c561934e089/System.Data.Entity.dll
----------------------------------------
System.Runtime.Serialization
    Assembly Version: 4.0.0.0
    Win32 Version: 4.0.30319.17929 built by: FX45RTMREL
    CodeBase: file:///C:/Windows/Microsoft.Net/assembly/GAC_MSIL/System.Runtime.Serialization/v4.0_4.0.0.0__b77a5c561934e089/System.Runtime.Serialization.dll
----------------------------------------
System.ComponentModel.DataAnnotations
    Assembly Version: 4.0.0.0
    Win32 Version: 4.0.30319.17929
    CodeBase: file:///C:/Windows/Microsoft.Net/assembly/GAC_MSIL/System.ComponentModel.DataAnnotations/v4.0_4.0.0.0__31bf3856ad364e35/System.ComponentModel.DataAnnotations.dll
----------------------------------------
Microsoft.SqlServer.Types
    Assembly Version: 11.0.0.0
    Win32 Version: 2011.0110.2100.060 ((SQL11_RTM).120210-1917 )
    CodeBase: file:///C:/Windows/assembly/GAC_MSIL/Microsoft.SqlServer.Types/11.0.0.0__89845dcd8080cc91/Microsoft.SqlServer.Types.dll
----------------------------------------

************** JIT Debugging **************
To enable just-in-time (JIT) debugging, the .config file for this
application or computer (machine.config) must have the
jitDebugging value set in the system.windows.forms section.
The application must also be compiled with debugging
enabled.

For example:

<configuration>
    <system.windows.forms jitDebugging="true" />
</configuration>

When JIT debugging is enabled, any unhandled exception
will be sent to the JIT debugger registered on the computer
rather than be handled by this dialog box.

如何摆脱这个问题？我试图通过简单的方法 db.savechanges() 解决这个问题，但它不起作用。

Answer 1

Unable to update the EntitySet because it has a DefiningQuery and no element exists in the element to support the current operation.

确保您的表有主键!

如果没有添加主键并更新 Entity Framework 模型并再次运行。

Source: