使用 CSharpCodeProvider 生成 DbContext

Question

使用以下代码，我在运行时生成OnlineShopContext

           string code = @"
           using System.Data.Entity;
           using GenerateContext.Models;
           using System.Data.Entity.Core.EntityClient;
           using GenerateContext.Models.Mapping;
           namespace GenerateContext.Models
           {
public partial class OnlineShopContext : DbContext
{
    static OnlineShopContext()
    {
        Database.SetInitializer<OnlineShopContext>(null);
    }
    public OnlineShopContext()
        : base(""Name = OnlineShopContext"")
    {
        }
  public DbSet<Customer> Customers { get; set; }
    public DbSet<Order> Orders { get; set; }
    public DbSet<OrderItem> OrderItems { get; set; }
    public DbSet<Product> Products { get; set; }

    protected override void OnModelCreating(DbModelBuilder modelBuilder)
    {
        modelBuilder.Configurations.Add(new CustomerMap());
        modelBuilder.Configurations.Add(new OrderMap());
        modelBuilder.Configurations.Add(new OrderItemMap());
        modelBuilder.Configurations.Add(new ProductMap());
    }
}
}
";
        CSharpCodeProvider provider = new CSharpCodeProvider();
        CompilerParameters parameters = new CompilerParameters();
        // Reference to System.Drawing library
        parameters.ReferencedAssemblies.Add("System.Drawing.dll");
        parameters.ReferencedAssemblies.Add("System.Data.dll");
        parameters.ReferencedAssemblies.Add("System.Data.Entity.dll");
        parameters.ReferencedAssemblies.Add("System.ComponentModel.dll");
      parameters.ReferencedAssemblies.Add(typeof(Customer).Assembly.Location);
                       parameters.ReferencedAssemblies.Add(typeof(CustomerMap).Assembly.Location);
                       parameters.ReferencedAssemblies.Add(typeof(DbSet).Assembly.Location);
                       parameters.ReferencedAssemblies.Add(typeof(DbContext).Assembly.Location);
                       parameters.ReferencedAssemblies.Add(typeof(IQueryable).Assembly.Location);
                                      parameters.ReferencedAssemblies.Add(typeof(IQueryable<>).Assembly.Location);
                       parameters.ReferencedAssemblies.Add(typeof(System.ComponentModel.IListSource).Assembly.Location);
        parameters.GenerateExecutable = false;
        parameters.GenerateInMemory = false;
        parameters.OutputAssembly = "OutputAssembly.dll";
        CompilerResults results = provider.CompileAssemblyFromSource(parameters, code);
        if (results.Errors.HasErrors)
        {
            StringBuilder sb = new StringBuilder();
            foreach (CompilerError error in results.Errors)
            {
                sb.AppendLine(String.Format("Error ({0}): {1}", error.ErrorNumber, error.ErrorText));
            }
            throw new InvalidOperationException(sb.ToString());
        }

并且生成的程序集:(使用 ILSpy）

using GenerateContext.Models.Mapping;
using System;
using System.Data.Entity;
namespace GenerateContext.Models
{
public class OnlineShopContext : DbContext
{
    public DbSet<Customer> Customers
    {
        get;
        set;
    }
    public DbSet<Order> Orders
    {
        get;
        set;
    }
    public DbSet<OrderItem> OrderItems
    {
        get;
        set;
    }
    public DbSet<Product> Products
    {
        get;
        set;
    }
    static OnlineShopContext()
    {
        Database.SetInitializer<OnlineShopContext>(null);
    }
    public OnlineShopContext() : base("Name = OnlineShopContext")
    {
    }
    protected override void OnModelCreating(DbModelBuilder modelBuilder)
    {
        modelBuilder.Configurations.Add<Customer>(new CustomerMap());
        modelBuilder.Configurations.Add<Order>(new OrderMap());
        modelBuilder.Configurations.Add<OrderItem>(new OrderItemMap());
        modelBuilder.Configurations.Add<Product>(new ProductMap());
    }
}

}

当我想创建实例并运行查询时，例如 FirstOrDeafult 或 Where， 这些方法不存在。 但是有一个 Find 方法由于数据类型不匹配而无法运行

        Assembly assembly = results.CompiledAssembly;
        Type type = assembly.GetType("GenerateContext.Models.OnlineShopContext");
        dynamic db = (DbContext)Activator.CreateInstance(type);
        var obj = db.Customers.GetType();
        MethodInfo main = obj.GetMethod("Find");
        object[] parametersArray = new object[] { 100 };
        var customer = main.Invoke(obj, parametersArray);

我该怎么做？如何将实例强制转换为类型并使用它强类型以使用 Where 或 FirstOrDefault 获取数据

Answer 1

如果我投射 db。客户System.Data.Entity.DbSet<Customer>它的工作原理。像下面一样

        var dllversionAssm = Assembly.LoadFile(@debugPath+"OutputAssembly.dll");
        Type type = dllversionAssm.GetType("GenerateContext.Models.OnlineShopContext");
        dynamic db = (DbContext)Activator.CreateInstance(type);
        var customerService  = ((System.Data.Entity.DbSet<Customer>)db.Customers);
        var customer = customerService.FirstOrDefault(q => q.Id == 100);

现在，如何将任何动态类型强制转换为其实体类型，例如 db。订单到System.Data.Entity.DbSet<Order>或数据库。产品要System.Data.Entity.DbSet<Product> .我的意思是我怎样才能有一个通用的方法来做到这一点？

Answer 2

最后我做到了.

    public System.Data.Entity.DbSet<T> Get<T>() where T : class
    {
        var dllversionAssm = Assembly.LoadFile(debugPath+"OutputAssembly.dll");
        Type type = dllversionAssm.GetType("GenerateContext.Models.OnlineShopContext");
        DbContext db = (DbContext)Activator.CreateInstance(type);
        var set = db.Set<T>();
        return set;
    }