從Web項目之外的程序集中獲取類

Question

我正在使用ASP.NET MVC 4，C#和AutoMapper。在我的global.asax.cs中，我試圖從另一個項目（我的web應用中引用的C＃項目）註冊我的映射。

在另一個項目，我有我的映射，這裏是一個示例類：

namespace MyProject.Web.Core.Mappings 
{ 
    public class EmployeeMapping 
    { 
      public EmployeeMapping() 
      { 
       Mapper.CreateMap<Employee, EmployeeInfoViewModel>(); 
      } 
    } 
} 

在我的global.asax.cs我有，我想加載這些映射的方法。下面我的代碼了網上，但它沒有拿起我的映射類，在這種情況下EmployeeMapping：

protected void AutoMapperConfig() 
{ 
    string mappingNamespace = "MyProject.Web.Core.Mappings"; 

    var q = from t in Assembly.GetAssembly(typeof(string)) 
      where t.IsClass && t.Namespace == mappingNamespace 
      select t; 

    q.ForEach(t => Debug.WriteLine(t.Name)); 
} 

如何讓我的班在特定的命名空間（從非Web項目以外的其他項目）和使用Activator.CreateInstance？

我想要的只是在給定的命名空間中指定的類的列表。

Answer 1

如何獲得我的類在特定的命名空間（從另一個項目以外的其他項目），並使用Activator.CreateInstance？

假設你知道在裝配的類型一個，你可以使用：

var types = typeof(TheTypeYouKnowAbout).Assembly.GetTypes() 
       .Where(t => t.Namespace == "TheNamespaceYouWant"); 
       // Possibly add more restrictions, e.g. it must be 
       // public, and a class rather than an interface, and 
       // must have a public parameterless constructor... 
foreach (var type in types) 
{ 
    // Do something with the type 
} 

（如果你可以給你想要做什麼的更多信息，它會更容易以更詳細地幫助您。）

Answer 2

當調用Assembly.GetAssembly(typeof(string))時，它將加載mscorlib.dll中的類型，並且不會從您提供的linq查詢返回任何內容。您需要使用typeof(EmployeeMapping).Assembly或Assembly.GetAssembly(typeof(EmployeeMapping))或Assembly.LoadFrom("YourAssemblyName.dll")加載程序集，以便查詢該特定程序集的類型。

編輯：

爲了進一步回答你的問題......假設你知道所有負責映射，它們都包含在組件類型

protected void AutoMapperConfig() 
{ 
    const string mappingNamespace = "MyProject.Web.Core.Mappings"; 

    //There are ways to accomplish this same task more efficiently. 
    var q = (from t in Assembly.LoadFrom("YourAssemblyName.dll").GetExportedTypes() 
      where t.IsClass && t.Namespace == mappingNamespace 
      select t).ToList(); 

    //Assuming all the types in this namespace have defined a 
    //default constructor. Otherwise, this iterative call will 
    //eventually throw a TypeLoadException (I believe) because 
    //the arguments for any of the possible constructors for the 
    //type were not provided in the call to Activator.CreateInstance(t) 
    q.ForEach(t => Activator.CreateInstance(t)); 
} 

但如果你是在Web項目中引用程序集......如果類型在編譯時是未知的，我會使用下面的或某種IoC/DI框架來實例化映射類。

protected void AutoMapperConfig() 
{ 
    Mapper.CreateMap<Employee, EmployeeInfoViewModel>(); 
    //Repeat the above for other "mapping" classes. 
    //Mapper.CreateMap<OtherType, OtherViewModel>(); 
} 

編輯鑑於第一@Brendan福格特的評論：

public interface IMappingHandler 
{ 
} 

//NOTE: None of this code was tested...but it'll be close(ish).. 

protected void AutoMapperConfig() 
{ 
    //If the assemblies are located in the bin directory: 
    var assemblies = Directory.GetFiles(HttpRuntime.BinDirectory, "*.dll"); 

    //Otherwise, use something like the following: 
    var assemblies = Directory.GetFiles("C:\\SomeDirectory\\", "*.dll"); 

    //Define some sort of other filter...a base type for example. 
    var baseType = typeof(IMappingHandler); 

    foreach (var file in assemblies) 
    { 
     //There are other ways to optimize this query. 
     var types = (from t in Assembly.LoadFrom(file).GetExportedTypes() 
        where t.IsClass && !t.IsAbstract && baseType.IsAssignableFrom(t) 
        select t).ToList(); 

     //Assuming all the queried types defined a default constructor. 
     types.ForEach(t => Activator.CreateInstance(t)); 
    } 
}