如何根据类型加载用户控件

Question

如果你有类型（即typeof(MyUserControl)），有没有办法实例化和使用usercontrol（.ascx）？

使用常规的asp.net控件（如文本框或下拉列表），您只需创建一个新实例并将其添加到控件集合中。这似乎不适用于用户控件。虽然您可以创建一个新实例并将其添加到集合中，并且触发所有事件，但它实际上不会呈现给页面。通常，您可以使用.ascx

的路径调用Page.LoadControl()

如果您拥有所有类型，则会出现问题。如何获得.ascx的路径以提供LoadControl方法。理想情况下，我还希望不必引用Page对象

Answer 1

没有。这不可能;必须提供ASCX虚拟路径以动态加载带有标记的用户控件，并且没有虚拟路径类型的内部映射。

但是，因为我仍然是懒惰的，所以我使用的方法仍然是“类型安全”，并将解决问题隔离到代码中的单个位置。它仍然需要访问“页面对象”，否则会处理愚蠢的细节。

以下是简要说明：

1. 使用类型查找相对（到我的根）ASCX路径，使用启发式将类型从命名空间映射到虚拟路径;允许一种指定手动映射的方法，并在指定时使用
2. 将类型的相对路径转换为正确/完整的虚拟路径
3. 使用虚拟路径加载控件
4. 继续，好像什么也没发生

享受（我只是从我的项目中复制'n'pasted部分，YMMV）：

    /// <summary>
    /// Load the control with the given type.
    /// </summary>
    public object LoadControl(Type t, Page page)
    {
        try
        {
            // The definition for the resolver is in the next code bit
            var partialPath = resolver.ResolvePartialPath(t);
            var fullPath = ResolvePartialControlPath(partialPath);
            // Now we have the Control loaded from the Virtual Path. Easy.
            return page.LoadControl(fullPath);
        } catch (Exception ex)
        {
            throw new Exception("Control mapping failed", ex);
        }
    }

    /// <summary>
    /// Loads a control by a particular type.
    /// (Strong-typed wrapper for the previous method).
    /// </summary>
    public T LoadControl<T>(Page page) where T : Control
    {
        try
        {
            return (T)LoadControl(typeof (T), page);
        } catch (Exception ex)
        {
            throw new Exception(string.Format(
                "Failed to load control for type: {0}",
                typeof (T).Name), ex);
        }
    }

    /// <summary>
    /// Given a partial control path, return the full (relative to root) control path.
    /// </summary>
    string ResolvePartialControlPath(string partialPath)
    {
        return string.Format("{0}{1}.ascx",
            ControlPathRoot, partialPath);
    }

ControlResolver的代码清单：

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;

namespace FooBar
{
    class ControlResolver
    {
        const string BaseNamespace = "TheBaseControlNameSpace";

        readonly IDictionary<Type, string> resolvedPaths = new Dictionary<Type, string>();

        /// <summary>
        /// Maps types to partial paths for controls.
        /// 
        /// This is required for Types which are NOT automatically resolveable
        /// by the simple reflection mapping.
        /// </summary>
        static readonly IDictionary<Type, string> MappedPartialPaths = new Dictionary<Type, string>
        {
            { typeof(MyOddType), "Relative/ControlPath" }, // No virtual ~BASE, no .ASXC
        };

        /// <summary>
        /// Given a type, return the partial path to the ASCX.
        /// 
        /// This path is the path UNDER the Control Template root
        /// WITHOUT the ASCX extension.
        /// 
        /// This is required because there is no mapping maintained between the class
        /// and the code-behind path.
        /// 
        /// Does not return null.
        /// </summary>
        public string ResolvePartialPath (Type type)
        {
            if (type == null)
            {
                throw new ArgumentNullException("type");
            }

            string partialPath;
            if (resolvedPaths.TryGetValue(type, out partialPath))
            {
                return partialPath;
            } else
            {
                string mappedPath;
                if (MappedPartialPaths.TryGetValue(type, out mappedPath))
                {
                    resolvedPaths[type] = mappedPath;
                    return mappedPath;
                } else
                {
                    // Since I use well-mapped virtual directory names to namespaces,
                    // this gets around needing to manually specify all the types above.
                    if (!type.FullName.StartsWith(BaseNamespace))
                    {
                        throw new InvalidOperationException("Invalid control type");
                    } else
                    {
                        var reflectionPath = type.FullName
                            .Replace(BaseNamespace, "")
                            .Replace('.', '/');
                        resolvedPaths[type] = reflectionPath;
                        return reflectionPath;
                    }
                }
            }
        }
    }
}

Answer 2

  ' Load the control 
  Dim myUC as UserControl = LoadControl("ucHeading.ascx") 

  ' Set the Usercontrol Type 
  Dim ucType as Type = myUC.GetType() 

  ' Get access to the property 
  Dim ucPageHeadingProperty as PropertyInfo = ucType.GetProperty("PageHeading") 

  ' Set the property 
  ucPageHeadingProperty.SetValue(myUC,"Access a Usercontrol from Code Behind",Nothing) 

  pnlHeading.Controls.Add ( myUC ) 

Answer 3

你可能在这里运气不好。

This fellow无法获得帮助。

他们告诉this person它无法完成。