If-Modified-Since in Asp.Net Web Api 2

Question

In my current project I'm using Angularjs with Asp.net Web Api 2 and trying to use some headers to determine workflow.

In one situation I want to update an entity only if "If-Modified-Since"-header is set and the value is the same as the stored entity.

My angular code looks like following:

$http.patch(selfLink, {message: item.message},
    {
        headers: {
            "Accept": "application/json",
            "Content-Type": "application/json",
            "If-Modified-Since": item.LastModified
        }
    }
)
.success(function(data, status, headers, config) {
    if (successCallback) {
        successCallback();
    }
})
.error(function(data, status, headers, config) {
    if (errorCallback) {
        errorCallback(data, status);
    }
});

The Web Api code looks like following:

public async Task<IHttpActionResult> Patch(int id, JObject updateEntity)
{
    using(var session = this.store.OpenAsyncSession())
    {
        var entity = await session.LoadAsync<TEntity>(id);
        if(entity == null)
        {
            return NotFound();
        }

        if(Request.Headers.IfModifiedSince.HasValue == false)
        {
            return BadRequest("Missing If-Modified-Since header");
        }

        // More code
    }

}

Every request I make I will get Request.Headers.IfModifiedSince.HasValue == false , but then I'm trying Request.Headers.GetValue("If-Modified-Since") I will get the value I'm asking for.

Does anyone know why the Request.Headers.IfModifiedSince property is not set?

Answer 1

Check the date format that you're sending as the header value. The date must be formatted according to the RFC 1123 standard. If

Request.Headers.GetValue("If-Modified-Since")

is not in this format, that would explain why

Request.Headers.IfModifiedSince

is null.