VirtualPathProvider.GetCacheDependency(String, IEnumerable, DateTime) Method

Definition

Namespace:

System.Web.Hosting

Assembly:

System.Web.dll

Creates a cache dependency based on the specified virtual paths.

C#

public virtual System.Web.Caching.CacheDependency GetCacheDependency(string virtualPath, System.Collections.IEnumerable virtualPathDependencies, DateTime utcStart);

Parameters

virtualPath

String

The path to the primary virtual resource.

virtualPathDependencies

IEnumerable

An array of paths to other resources required by the primary virtual resource.

utcStart

DateTime

The UTC time at which the virtual resources were read.

Returns

CacheDependency

A CacheDependency object for the specified virtual resources.

Examples

The following code example implements the GetCacheDependency method for a custom VirtualPathProvider class. For the full code required to run the example, see the Example section of the VirtualPathProvider class overview topic.

C#

public override CacheDependency GetCacheDependency(
  string virtualPath, 
  System.Collections.IEnumerable virtualPathDependencies, 
  DateTime utcStart)
{
  if (IsPathVirtual(virtualPath))
  {
    System.Collections.Specialized.StringCollection fullPathDependencies = null;

    // Get the full path to all dependencies.
    foreach (string virtualDependency in virtualPathDependencies)
    {
      if (fullPathDependencies == null)
        fullPathDependencies = new System.Collections.Specialized.StringCollection();

      fullPathDependencies.Add(virtualDependency);
    }
    if (fullPathDependencies == null)
      return null;

    // Copy the list of full-path dependencies into an array.
    string[] fullPathDependenciesArray = new string[fullPathDependencies.Count];
    fullPathDependencies.CopyTo(fullPathDependenciesArray, 0);
    // Copy the virtual path into an array.
    string[] virtualPathArray = new string[1];
    virtualPathArray[0] = virtualPath;

    return new CacheDependency(virtualPathArray, fullPathDependenciesArray, utcStart);
  }
  else
        {
            return Previous.GetCacheDependency(virtualPath, virtualPathDependencies, utcStart);
        }
    }

Remarks

The default implementation of the GetCacheDependency method returns null. To cache virtual resources for later use you must override either the GetCacheDependency method or the GetFileHash method.

Applies to