Question

这让我很生气。我是WPF / EF的新手。

我有一个简单的MVVM应用程序，它通过XAML中的绑定将实体表读入DataGrid。该应用程序编译好。

我得到了这个未处理的异常但却锁定了设计师：

The specified named connection is either not found in the configuration, not intended to be used with the EntityClient provider, or not valid.
at System.Data.EntityClient.EntityConnection.ChangeConnectionString(String newConnectionString)
at System.Data.EntityClient.EntityConnection..ctor(String connectionString)
at System.Data.Objects.ObjectContext.CreateEntityConnection(String connectionString)

XAML无法创建我的View Model的实例......

xmlns:vm="clr-namespace:Entity_MVVM"
    Title="MainWindow" Height="600" Width="800"
    DataContext="{DynamicResource MyViewModel}">
<Window.Resources>
    <vm:CountrysViewModel x:Key="MyViewModel"/>
</Window.Resources>

这是我的视图模型'加载网格'方法：

 public void LoadGrid()

    {
        var db = new LDBEntities();
        using (var conn = new EntityConnection("name=LDBEntities"))
        {
            conn.Open();
            EntityCommand cmd = conn.CreateCommand();
            cmd.CommandText = "SELECT VALUE c FROM LDBEntities.tbCountrys as c";

            try
            {
                EntityDataReader rdr = cmd.ExecuteReader(CommandBehavior.SequentialAccess | CommandBehavior.CloseConnection);

                _CountrysModelObservableList.Clear();

                while (rdr.Read())
                {
                    var cCountryId = rdr["CountryId"].ToString();
                    var cShortName = rdr["shortName"].ToString();
                    var cLongName = rdr["longName"].ToString();

                    _CountrysModelView = new CountrysModel()
                    {
                        CountryId = cCountryId,
                        ShortName = cShortName,
                        LongName = cLongName
                    };

                    _CountrysModelObservableList.Add(_CountrysModelView);
                }
            }
            catch(Exception e)
            {
                MessageBox.Show(string.Format("Can't read in data!"));
            }
        }

我的App.config中的连接字符串是在创建我的EF模型时创建的，并按预期填充DataGrid。

任何想法导致了什么？

周五下午沮丧！感谢

编辑：App.Config：

<?xml version="1.0" encoding="utf-8"?>
<configuration>
<connectionStrings>
<add name="LDBEntities" connectionString="metadata=res://*/DataModel.csdl|res://*/DataModel.ssdl|res://*/DataModel.msl;provider=System.Data.SqlClient;provider connection string='Data Source=DMEA-T1000\SQLEXPRESS;Initial Catalog=LDB;Persist Security Info=True;User ID=sa;Password=PasswordHidden;MultipleActiveResultSets=True' " providerName="System.Data.EntityClient" /></connectionStrings>
</configuration>

Answer 1

将ERM添加到项目时，它将为您创建模型。

如果您的数据库中有一个名为tblYears的表，您应该可以声明：

tblYear y = new tblYear();

我个人创建了一个本地模型并填充它以在视图中使用，即viewmodel。

class YearModel : INotifyPropertyChanged
{

#region Members

    MyERM.tblYear _year;

#endregion

#region Properties

    public MyERM.tblYear Year
    {
        get { return _year; }
    }

    public Int32 id
    {
        get { return Year.id; }
        set
        {
            Year.id = value;
            NotifyPropertyChanged("id");
        }
    }

    public String Description
    {
        get { return Year.Description; }
        set
        {
            Year.Description = value;
            NotifyPropertyChanged("Description");
        }
    }

#endregion

#region Construction

    public YearModel()
    {
        this._year = new MyERM.Year
        {
            id = 0,
            Description = ""
        };
    }

#endregion
}

然后，您可以使用此视图模型填充List＆lt;＆gt;或作为单独的记录 - 列表示例：

class YearListModel
{
    myERM db = new myERM();

    #region Members

    private ObservableCollection<YearModel> _years;

    #endregion

    #region Properties

    public ObservableCollection<YearModel> Years
    {
        get { return _years; }
    }

    #endregion

    #region Construction

    public YearListModel()
    {
        _years = new ObservableCollection<YearModel>();

        foreach (MyERM.tblYear y in db.tblYears())
        {
            _years.Add(new YearModel
            {
                id = y.id,
                Description = y.Description
            }
          );
        }
    }

    #endregion
}

然后，例如，您可以将其发送到如下页面：

xmlns:local="clr-namespace:MyProject.ViewModels"

<Page.Resources>
    <local:YearListModel x:Key="YearList" />
</Page.Resources>

并将其绑定到控件：

<ListView x:Name="listviewname"
          DataContext="{StaticResource ResourceKey=YearList}"
          ItemsSource="{Binding Path=Years}">
    <ListView.View>
        <GridView>
            <GridViewColumn x:Name="columnname" Header="Code" 
                            DisplayMemberBinding="{Binding Code}"/>
        </GridView>
    </ListView.View>
</ListView>

希望这有助于GL

WPF中的MVVM与实体框架未处理的异常

1 个答案: