Activator.CreateInstance with param - 未找到 child class 类型的构造函数

Question

我尝试将 connectionString 传递给上下文工厂构造函数，但出现错误 "constructor type of ContextImplementationTest not found" 有什么问题？我打电话给

string bid="someCOnnectionString";
using (BaseContext<DbContext> db = MediaDbContext.GetBidContext(bid)){...}


public static class MediaDbContext
{
   public static BaseContext<DbContext> GetBidContext(string connString)
    {
        //Settings.ContextFactory="ContextImplementationTest"
        Type contextFactoryType = Type.GetType("Media.DB.Context.Implementation." + Settings.ContextFactory);
        object[] args = new object[] { connString};
        BaseContext<DbContext> instance = (BaseContext<DbContext>)Activator.CreateInstance(contextFactoryType, args);
        return instance;
    }
}

基础Class

public class BaseContext<TContext> : DbContext where TContext : DbContext
{
    static BaseContext()
    {
        Database.SetInitializer<TContext>(null);
    }

    protected BaseContext(string connectionString) : base(connectionString)
    {
    }...

Child class

public class ContextImplementationTest : BaseContext<DbContext>
{
    protected override void OnModelCreating(DbModelBuilder modelBuilder)
    {...}

更新：要调用 child class 中的构造函数，您需要在此 class 中有构造函数。

Child class

public class ContextImplementationTest : BaseContext<DbContext>
{
   protected ContextImplementationTest(string connectionString) : base(connectionString)
   {
   }...

Answer 1

Activator.CreateInstance 仅在默认构造函数调用的情况下采用 nonPublic 参数。

您可以使用 Type.GetConstructor 代替：

Type contextFactoryType = 
    Type.GetType("Media.DB.Context.Implementation." + Settings.ContextFactory);

ConstructorInfo ci = contextFactoryType .GetConstructor(
    BindingFlags.Instance | BindingFlags.NonPublic,
    binder: null, new Type[] { typeof(string) }, modifiers: null);

object[] args = new object[] { connString };

var instance = (BaseContext<DbContext> instance)ci.Invoke(args);
return instance;

Activator.CreateInstance with param - 未找到 child class 类型的构造函数

Activator.CreateInstance with param - constructor of child class type not found

.net

c#

activator