实体框架，ASP.NET，上下文缺失

Question

I'm new here (and still rookie coding), so sorry, if I asking wrong or stupid... I'm trying to go through with Troelsen's book Pro C# 7 with .NET and .NET Core, but I stuck at the begining of chapter 29. The main goal is to create an ASP.NET MVC (named CarLotMVC) solution. I'm created the ASP project, as the book said, and then I try to insert two other projects (AutoLotDAL and AutoLotDAL.Models). I'm doing exactly like it is written in the book, but when I try to add a new Controller to the ASP project, I can't see the context, and only seeing the ASP projects model classes. I downloaded the source code, added the AutoLotDAL and AutoLotDAL.Models projects to the solution, modified the connection strings, the namespaces, but still can't see the context, or the model classes.

Scaffolds menu - missing models

What could be wrong? In the AutoLotDAL project there are the migration classes, I tried to delete the database and create again, but that did'n help. Try to run Visual Studio with administrator, clean the solution and build again. I saw only once the context, there were multiple errors in the solution, the VS created the Controller class without my help, but when I reopened later the solution all was gone.

this is the context:

public partial class AutoLotEntities : DbContext
{
    public AutoLotEntities()
        : base("name=AutoLot")
    {
    }

    protected override void Dispose(bool disposing)
    {
    }

    private void OnSavingChanges(object sender, EventArgs eventArgs)
    {
        var context = sender as ObjectContext;
        if (context == null) return;
        foreach (ObjectStateEntry item in
            context.ObjectStateManager.GetObjectStateEntries(EntityState.Modified | EntityState.Added))
        {
            if ((item.Entity as Inventory) != null)
            {
                var entity = (Inventory)item.Entity;
                if (entity.Color == "Red")
                {
                    item.RejectPropertyChanges(nameof(entity.Color));
                }
            }
        }

    }

    private void OnObjectMaterialized(object sender, ObjectMaterializedEventArgs e)
    {
    }

    public virtual DbSet<CreditRisk> CreditRisks { get; set; }
    public virtual DbSet<Customer> Customers { get; set; }
    public virtual DbSet<Inventory> Cars { get; set; }
    public virtual DbSet<Order> Orders { get; set; }

    protected override void OnModelCreating(DbModelBuilder modelBuilder)
    {
        modelBuilder.Entity<Inventory>()
            .HasMany(e => e.Orders)
            .WithRequired(e => e.Car)
            .WillCascadeOnDelete(false);
    }
}

This is the connectionString:

<connectionStrings> <add name="AutoLot" connectionString="data source=(local)\SQLEXPRESS;initial catalog=AutoLot;integrated security=True;MultipleActiveResultSets=True;App=EntityFramework" providerName="System.Data.SqlClient" /> </connectionStrings>    

I'm using VS Community 2017, .NET Framework 4.6.1, EF 6.2.0, updated all NuGet packages. But still can't reproduce the solution in the book... Please help.

The references list: References branch

Answer 1

I found a way around this by copying a section in the CarLotMVC.csproj file from the book's solution into my project.

Start by navigating to the ..\\pro-csharp-7-master\\Chapter_29\\CarLotMVC\\CarLotMVC directory in the book's solution code and opening the CarLotMVC.csproj file in a text editor.

Locate the following element and copy it to the clipboard:

  <ItemGroup>
    <ProjectReference Include="..\AutoLotDAL.Models\AutoLotDAL.Models.csproj">
      <Project>{9a917d7c-885e-4d9a-818f-9955871a4fbb}</Project>
      <Name>AutoLotDAL.Models</Name>
    </ProjectReference>
    <ProjectReference Include="..\AutoLotDAL\AutoLotDAL.csproj">
      <Project>{7e5a8812-c303-4ae0-a6e7-4ac96ec11624}</Project>
      <Name>AutoLotDAL</Name>
    </ProjectReference>
  </ItemGroup>

Confirm the project guid's match the guid's in your AutoLotDAL and AutoLotDAL.Models projects by opening the AutoLotDAL.csproj in the AutoLotDAL project and the AutoLotDAL.Models.csproj in the AutoLotDAL.csproj and comparing the ProjectGuid tags with the values specified in the element copied from the book's solution.

The following is line #7 from my AutoLotDAL.csproj:

<ProjectGuid>{7E5A8812-C303-4AE0-A6E7-4AC96EC11624}</ProjectGuid>

Go to your project's directory with the same file and open it in a text editor. Locate the following block (line #185 in my file):

  <ItemGroup>
    <Folder Include="App_Data\" />
    <Folder Include="Models\" />
  </ItemGroup>

and paste the element from the solution's file after it.

Now, locate the following elements in the same file (line #49 in my file):

    <Reference Include="AutoLotDAL">
      <HintPath>..\AutoLotDAL\bin\Debug\AutoLotDAL.dll</HintPath>
    </Reference>
    <Reference Include="AutoLotDAL.Models">
      <HintPath>..\AutoLotDAL.Models\bin\Debug\AutoLotDAL.Models.dll</HintPath>
    </Reference>

and comment out or delete the lines.

Save the file and try adding the controller again. The project worked for me with these changes.

Answer 2

In addition do adding the AutoLotDAL and the AutoLotDAL.Models Project to the solution, you have to add a reference to those projects in the CarLotMVC Project. You can find a documentation on that topic here .

After doing this you have to recompile your project. If it compiles without any errors, you should see the Context and Model classes in the scaffolding dialog.