HttpRequestHeaderCollection.IfModifiedSince Property

Definition

Namespace:

Windows.Web.Http.Headers

Gets or sets the DateTime object that represents the value of an If-Modified-Since HTTP header on an HTTP request.

public:
 property IReference<DateTime> ^ IfModifiedSince { IReference<DateTime> ^ get(); void set(IReference<DateTime> ^ value); };

IReference<DateTime> IfModifiedSince();

void IfModifiedSince(IReference<DateTime> value);

public System.Nullable<System.DateTimeOffset> IfModifiedSince { get; set; }

var iReference = httpRequestHeaderCollection.ifModifiedSince;
httpRequestHeaderCollection.ifModifiedSince = iReference;

Public Property IfModifiedSince As Nullable(Of DateTimeOffset)

Property Value

IReference<DateTime>

Nullable<DateTimeOffset>

The DateTime object that represents the value of an If-Modified-Since HTTP header on an HTTP request. A null value means that the header is absent.

Remarks

The IfModifiedSince property represents the value of an If-Modified-Since HTTP header on an HTTP request message. The If-Modified-Since header is the date and time the content was modified since.

Javascript and .NET languages do not use the DateTime object directly. In Javascript a DateTime is projected as a object, and in .NET it is projected as a System.DateTimeOffset. Each language transparently handles the conversion to the granularity and date ranges for the respective language.

In C++, a value has the same granularity as a and supports the date ranges required by Javascript and .NET.

For more detailed information, see the Windows.Foundation.DateTime structure.

The following sample code shows a method to set the If-Modified-Since header on an HttpRequestMessage object using the IfModifiedSince property on the HttpRequestHeaderCollection object.

public void DemonstrateHeaderRequestIfModifiedSince() {
    var request = new HttpRequestMessage();

    // This is not typically set with a string.

    // Set the header with a strong type.
    var value = DateTimeOffset.Now.AddDays(-1); // Since yesterday.
    request.Headers.IfModifiedSince = value;

    // Get the strong type out
    System.Diagnostics.Debug.WriteLine("IfModifiedSince value in ticks: {0}", request.Headers.IfModifiedSince.Value.Ticks);

    // The ToString() is useful for diagnostics, too.
    System.Diagnostics.Debug.WriteLine("The IfModifiedSince ToString() results: {0}", request.Headers.IfModifiedSince.ToString());
}

See also

• DateTime
• HttpRequestMessage
• Headers
• IfUnmodifiedSince