asp.net mvc(十一)自定义view engine

        当创建一个asp.net mvc 1.0的项目后,在web工程中都会出现Views文件夹,这里面就是我们存放View Page或者是partial view的地方。而且系统对于Controller的名称以及Views文件夹下面的子文件夹名称均有一定的约束。

        例如，有一个名称为GuestBookController的Controller,这时我们创建View Page时，就需要在Views下面创建一个GuestBook的子文件夹，不能随便命名。然后把View page或者是partial view放进来，或者把文件放在Shared文件夹中也行,如果把view page放在web工程根目录下面，系统会找不到对应的view。

        本文解决问题：针对上面的局限性，我们能不能打破呢？即可以实现如下功能：

        第一：view page可以放在views之外的文件夹中。

        第二：view page的名称和Controller的名称取消名称上的约束，例如：view page名称是ViewContentPage1.aspx,而对应的Controller名称是testController.cs。

        实现原理：asp.net mvc之所以能根据用户请求找到对应的view page，主要是路由。这其中有一个重要的类WebFormViewEngine,它负责发现我们创建的view page或者是partial view。为此我们可以重写一个新的ViewEngine来完成我的目的。

        1:先看下webformviewengine的构造函数：

代码

public  WebFormViewEngine()
{
     base .MasterLocationFormats  =   new   string [] {  " ~/Views/{1}/{0}.master " ,  " ~/Views/Shared/{0}.master "  };
     base .ViewLocationFormats  =   new   string [] {  " ~/Views/{1}/{0}.aspx " ,  " ~/Views/{1}/{0}.ascx " ,  " ~/Views/Shared/{0}.aspx " ,  " ~/Views/Shared/{0}.ascx "  };
     base .PartialViewLocationFormats  =   base .ViewLocationFormats;
}

        base.ViewLocationFormats 可以看出view page为什么只能写在views文件夹下的原因了。所以我们只需要在新的view engine的构造函数中修改下base.ViewLocationFormats 路径即可。这里我创建一个新的WebViewEngine,它需要继承WebFormViewEngine。可以这样改写：这样第一点就完成了。
   

代码

public  WebViewEngine()
        {
             base .MasterLocationFormats  =   new   string [] {  " ~/Views/{1}/{0}.master " ,  " ~/Views/Shared/{0}.master "  };
             base .ViewLocationFormats  =   new   string [] { 
                  " ~/com/{0}.aspx " ,
                 " ~/com/{0}.ascx " ,
                 " ~/Views/{1}/{0}.aspx " ,
                 " ~/Views/{1}/{0}.ascx " , 
                  " ~/Common/Views/{0}.aspx " ,
                " ~/Common/Views/{0}.ascx " ,
                 " ~/Views/Shared/{0}.aspx " ,
                 " ~/Views/Shared/{0}.ascx "  };
             base .PartialViewLocationFormats  =   base .ViewLocationFormats;
        }

         2:WebFormViewEngine有两个重要方法：FindPartialView以及FindView。它负责从用户请求以及路由配置中查找到具体的view page或者是partial view。第二点就可以在这下手。
         首先：我们需要修改下路由配置，增加一个参数viewpath,用来指定路由规则使用的view path路径。
      

代码

routes.MapRoute(
                 " Default2 " ,
                 " ViewContentPage1.aspx " ,
                 new  { id  =   "" , viewpath  =   " ~/com/ViewContentPage1.aspx " , controller  =   " test " , action  =   " test "  }
            );

        其次：修改下WebFormViewEngine的源码：这里主要是修改GetPath方法，它最终会返回一个view page的路径。这样我们就可以这样访问了http://www.testmy.com/guestbook/ViewContentPage1.aspx。
      

代码

public   override  ViewEngineResult FindPartialView(ControllerContext controllerContext,  string  partialViewName,  bool  useCache)
        {
             string [] strArray;
             if  (controllerContext  ==   null )
            {
                 throw   new  ArgumentNullException( " controllerContext " );
            }
             if  ( string .IsNullOrEmpty(partialViewName))
            {
                 throw   new  ArgumentException( " MvcResources.Common_NullOrEmpty " ,  " partialViewName " );
            }
             string  requiredString  =  controllerContext.RouteData.GetRequiredString( " controller " );
             // string vp = this.GetParam(controllerContext, "viewpath");
             // if (!string.IsNullOrEmpty(vp))
             // {
             //     requiredString = vp;
             // }
             string  str2  =   this .GetPath(controllerContext,  this .PartialViewLocationFormats,  " PartialViewLocationFormats " , partialViewName, requiredString,  " Partial " , 

useCache, false  ,  out  strArray);
             if  ( string .IsNullOrEmpty(str2))
            {
                 return   new  ViewEngineResult(strArray);
            }
             return   new  ViewEngineResult( this .CreatePartialView(controllerContext, str2),  this );

        }
         public   override  ViewEngineResult FindView(ControllerContext controllerContext,  string  viewName,  string  masterName,  bool  useCache)
        {
             string [] strArray;
             string [] strArray2;
             if  (controllerContext  ==   null )
            {
                 throw   new  ArgumentNullException( " controllerContext " );
            }
             if  ( string .IsNullOrEmpty(viewName))
            {
                 throw   new  ArgumentException( " ArgumentException " ,  " viewName " );
            }
             string  requiredString  =  controllerContext.RouteData.GetRequiredString( " controller " );
             // string vp=this.GetParam(controllerContext, "viewpath");
             // if (!string.IsNullOrEmpty(vp))
             // {
             //     requiredString = vp;
             // }
             string  str2  =   this .GetPath(controllerContext,  this .ViewLocationFormats,  " ViewLocationFormats " , viewName, requiredString,  " View " , useCache, true  ,  out  strArray);
             string  str3  =   this .GetPath(controllerContext,  this .MasterLocationFormats,  " MasterLocationFormats " , masterName, requiredString,  " Master " , useCache, true  ,  out  

strArray2);
             if  ( string .IsNullOrEmpty(str2)  ||  ( string .IsNullOrEmpty(str3)  &&   ! string .IsNullOrEmpty(masterName)))
            {
                 return   new  ViewEngineResult(strArray.Union < string > (strArray2));
            }
             return   new  ViewEngineResult( this .CreateView(controllerContext, str2, str3),  this );

        }
         private   string  GetParam(ControllerContext controllerContext,  string  key)
        {
             return  controllerContext.RouteData.Values[key]  !=   null   ?  controllerContext.RouteData.Values[key].ToString() :  string .Empty;
        }
         private   string  GetPath(ControllerContext controllerContext,  string [] locations,  string  locationsPropertyName,  string  name,  string  controllerName,  string  cacheKeyPrefix, 

bool  useCache,  bool  isfindview,  out   string [] searchedLocations)
        {
            searchedLocations  =  _emptyLocations;
             if  ( string .IsNullOrEmpty(name))
            {
                 return   string .Empty;
            }
             if  ((locations  ==   null )  ||  (locations.Length  ==   0 ))
            {
                 throw   new  InvalidOperationException( string .Format(CultureInfo.CurrentUICulture,  " MvcResources.Common_PropertyCannotBeNullOrEmpty " ,  new   object [] { 

locationsPropertyName }));
            }
             bool  flag  =  IsSpecificPath(name);
             string  key  =   this .CreateCacheKey(cacheKeyPrefix, name, flag  ?   string .Empty : controllerName);
             if  (useCache)
            {
                 string  viewLocation  =   this .ViewLocationCache.GetViewLocation(controllerContext.HttpContext, key);
                 if  (viewLocation  !=   null )
                {
                     return  viewLocation;
                }
            }
            
             return  (flag  ?   this .GetPathFromSpecificName(controllerContext, name, key,isfindview ,  ref  searchedLocations) :  this .GetPathFromGeneralName(controllerContext, 

locations, name, controllerName, key,isfindview ,  ref  searchedLocations));
        }
         private   string  CreateCacheKey( string  prefix,  string  name,  string  controllerName)
        {
             return   string .Format(CultureInfo.InvariantCulture,  " :ViewCacheEntry:{0}:{1}:{2}:{3}: " ,  new   object [] {  base .GetType().AssemblyQualifiedName, prefix, name, 

controllerName });
        }
         private   static   bool  IsSpecificPath( string  name)
        {
             char  ch  =  name[ 0 ];
             return  ((ch  ==   ' ~ ' )  ||  (ch  ==   ' / ' ));
        }
         private   string  GetPathFromSpecificName(ControllerContext controllerContext,  string  name,  string  cacheKey, bool  isfindview,  ref   string [] searchedLocations)
        {
             string  virtualPath  =  name;
             if  ( ! this .FileExists(controllerContext, name))
            {
                 if  (isfindview)
                {
                     string  vp  =   this .GetParam(controllerContext,  " viewpath " );
                     if  ( ! string .IsNullOrEmpty(vp))
                    {
                        virtualPath  =  vp;
                    }
                     if  ( string .IsNullOrEmpty(virtualPath))
                    {
                        virtualPath  =   string .Empty;
                        searchedLocations  =   new   string [] { name };
                    }
                }
                 else
                {
                    virtualPath  =   string .Empty;
                    searchedLocations  =   new   string [] { name };
 
                }
            }
             this .ViewLocationCache.InsertViewLocation(controllerContext.HttpContext, cacheKey, virtualPath);
             return  virtualPath;
        }
         private   string  GetPathFromGeneralName(ControllerContext controllerContext,  string [] locations,  string  name,  string  controllerName,  string  cacheKey,  bool  isfindview,  ref  

string [] searchedLocations)
        {
             string  virtualPath  =   string .Empty;
            searchedLocations  =   new   string [locations.Length];
             for  ( int  i  =   0 ; i  <  locations.Length; i ++ )
            {
                 string  str2  =   string .Format(CultureInfo.InvariantCulture, locations[i],  new   object [] { name, controllerName });
                 if  ( this .FileExists(controllerContext, str2))
                {
                    searchedLocations  =  _emptyLocations;
                    virtualPath  =  str2;
                     this .ViewLocationCache.InsertViewLocation(controllerContext.HttpContext, cacheKey, virtualPath);
                     return  virtualPath;
                }
                 else
                {
                     if  (isfindview)
                    {
                         string  vp  =   this .GetParam(controllerContext,  " viewpath " );
                         if  ( ! string .IsNullOrEmpty(vp))
                        {
                            searchedLocations  =  _emptyLocations;
                            virtualPath  =  vp;
                             return  virtualPath;
                        }
                    }

                }
                searchedLocations[i]  =  str2;
            }
             return  virtualPath;
        }

           最后：在程序中注册新的view engine:        

            //注册viewEngine
            ViewEngines.Engines.Clear();
            ViewEngines.Engines.Add(new  WebViewEngine());
            RegisterRoutes(RouteTable.Routes);

 

           总结：很久没有更新mvc的文章了,不过这篇在实际项目中还是非常有用的，例如，我们可以把两个不同的view page指定同一个Controller等等。

作者：姜敏
出处：http://www.cnblogs.com/aspnet2008/