无法将类型为'System.Data.Entity.Infrastructure.DbQuery`1 [ClaimBuildMVC.Models.UserDetail]'的对象强制转换为'System.Co

Question

我是使用LINQ使用Entity框架的MVC的新手，我收到了以下错误

  

无法将类型为'System.Data.Entity.Infrastructure.DbQuery 1 [BuildMVC.Models.UserDetail]'的对象转换为'System.Collections.Generic.IList`1 [System.Object]'

以下是代码

//Here is sample code :

public ActionResult CreatePieChart()
        {
            Bitmap bitmapImage = new Bitmap(450, 300);
            Graphics graphics = Graphics.FromImage(bitmapImage);
            MemoryStream imageStream = new MemoryStream();
            //Creating Chart Temaplate
            var PieChart = new System.Windows.Forms.DataVisualization.Charting.Chart();
            var PieChartArea = new System.Windows.Forms.DataVisualization.Charting.ChartArea();
            var Legend = new System.Windows.Forms.DataVisualization.Charting.Legend();
            Legend.Docking = System.Windows.Forms.DataVisualization.Charting.Docking.Bottom;
            var ChartSeries = new System.Windows.Forms.DataVisualization.Charting.Series();
            PieChart.Palette = System.Windows.Forms.DataVisualization.Charting.ChartColorPalette.None;
            var PieChartTitle = new System.Windows.Forms.DataVisualization.Charting.Title();
            PieChart.Location = new System.Drawing.Point(100, 10);
            PieChart.Size = new System.Drawing.Size(450, 300);
            PieChartArea.Name = "PieChartArea";
            Legend.Name = "Legend";
            PieChart.Name = "PieChart";
            PieChart.Text = "PieChart";
            PieChart.ChartAreas.Add(PieChartArea);
            PieChart.Legends.Add(Legend);

            //Initializing Chart Components
            List<string> ChartXValues = new List<string>(); //X Values
            List<Single> ChartYValues = new List<Single>(); //Y Values

            ChartSeries.ChartArea = PieChartArea.Name;
            ChartSeries.Legend = Legend.Name;
            ChartSeries.Name = PieChart.Name;
            PieChart.Series.Add(ChartSeries);
            PieChartTitle.Name = "PieChart";
            PieChartTitle.Text = "PieChart";
            //Data Binding
            PieChart.Series[ChartSeries.Name].Points.DataBindXY(ChartXValues, ChartYValues);
            PieChart.Series[ChartSeries.Name].ChartType = SeriesChartType.Pie;
            PieChart.Series[ChartSeries.Name].IsValueShownAsLabel = true;
            PieChart.Series[ChartSeries.Name].Label = "#VALY{##0.0}%";
            PieChart.Series[ChartSeries.Name].LabelForeColor = Color.White;

            PieChart.SaveImage(imageStream, ChartImageFormat.Png);
            PieChart.TextAntiAliasingQuality = TextAntiAliasingQuality.SystemDefault;
            Response.ContentType = "image/png";
            imageStream.WriteTo(Response.OutputStream);
            graphics.Dispose();
            bitmapImage.Dispose();
        }

//To Display in page :

<img src="@Url.Action("ActionName", "ControllerName") />

我从第二个表中获取public interface IGenericRepository<TEntity> where TEntity : class { IList<dynamic> GetRecord(long Id); void Add(TEntity entity); void update(TEntity entity); } public IList<dynamic> GetRecord(long Id) { var _lstUser=(IList<dynamic>)(from ud in _dbContext.UserDetails join rs in _dbContext.RolesMasters on ud.FkRoleId equals rs.ID select new UserDetail { FirstName = ud.FirstName + " " + ud.LastName, PostalStreet=rs.RoleName, IsDeleted=ud.IsDeleted }); return _lstUser; } 列，但由于我使用了rs.RoleName类，所以我从UserDetail获取了PostalStreet列，不知道这是是否正确。

Answer 1

 public static IEnumerable<CustomerOrder> GetCustomerOrder(this IRepository<Customer> repository, string country)
    {
        var customers = repository.GetRepository<Customer>().Queryable();
        var orders = repository.GetRepository<Order>().Queryable();
        var query = from c in customers
            join o in orders on new {a = c.CustomerID, b = c.Country}
                equals new {a = o.CustomerID, b = country}
            select new CustomerOrder
            {
                CustomerId = c.CustomerID,
                ContactName = c.ContactName,
                OrderId = o.OrderID,
                OrderDate = o.OrderDate
            };

        return query.AsEnumerable();
    }

这里我创建了一个额外的类，它将包含两个在WebGrid中使用的类的变量。