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CacheDependency Constructor (String[], DateTime)

Initializes a new instance of the CacheDependency class that monitors an array of paths (to files or directories) for changes and specifies a time when change monitoring begins.

Namespace:  System.Web.Caching
Assembly:  System.Web (in System.Web.dll)

public CacheDependency(
	string[] filenames,
	DateTime start


Type: System.String[]

An array of paths (to files or directories) that the cached object is dependent upon. When any of these resources changes, the cached object becomes obsolete and is removed from the cache.

Type: System.DateTime

The time against which to check the last modified date of the objects in the array.

If any of the directories or files specified in the filenames parameter is not found in the file system, it is treated as missing. If a directory or file is missing when the object with the dependency is added to the Cache, the cached object will be removed from the Cache when that directory or file is created.

For example, assume that you add an object to the Cache with a dependency on the following file path: c:\stocks\xyz.dat. If that file is not found when the CacheDependency object is created, but is created later, the cached object is removed upon the creation of the xyz.dat file.


Change tracking begins immediately and is not directly based on the start parameter. Use the start parameter to pass a date and time in the past against which you want to check the last modified date of the array passed in the filenames parameter. If the last modified date of any object in the array is later than the date and time set passed in the start parameter, the cached item is removed from the Cache.

The following code example creates a CacheDependency object that passes two XML files and a DateTime.Now value when the object is included as a parameter argument in an Cache.Insert method call.

// Create a DateTime object that determines
// when dependency monitoring begins.
DateTime dt = DateTime.Now;
    // Make key1 dependent on several files.
    String[] files = new String[2];
    files[0] = Server.MapPath("isbn.xml");
    files[1] = Server.MapPath("customer.xml");
    CacheDependency dep = new CacheDependency(files, dt);

    Cache.Insert("key1", "Value 1", dep);

.NET Framework

Supported in: 4.5, 4, 3.5, 3.0, 2.0, 1.1, 1.0

Windows 8.1, Windows Server 2012 R2, Windows 8, Windows Server 2012, Windows 7, Windows Vista SP2, Windows Server 2008 (Server Core Role not supported), Windows Server 2008 R2 (Server Core Role supported with SP1 or later; Itanium not supported)

The .NET Framework does not support all versions of every platform. For a list of the supported versions, see .NET Framework System Requirements.

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