/// <summary>
/// Generates a fully qualified URL to the specified attachment. If the attachment is an image, the URL points to a resized version.
/// </summary>
/// <param name="instance">The object that provides methods to build URLs to Kentico content.</param>
/// <param name="attachment">The attachment.</param>
/// <param name="constraint">The size constraint that is enforced on image when resizing.</param>
/// <param name="options">Options that affect the attachment URL.</param>
/// <returns>The fully qualified URL to the attachment.</returns>
/// <exception cref="ArgumentNullException"><paramref name="instance"/> or <paramref name="attachment"/> is null.</exception>
public static string Attachment(this ExtensionPoint<UrlHelper> instance, Attachment attachment, SizeConstraint constraint, AttachmentUrlOptions options = null)
{
if (instance == null)
{
throw new ArgumentNullException("instance");
}
if (attachment == null)
{
throw new ArgumentNullException("attachment");
}
return GenerateAttachmentUrl(instance, attachment, constraint, options);
}
private static string GenerateAttachmentUrl(ExtensionPoint<UrlHelper> instance, Attachment attachment, SizeConstraint constraint, AttachmentUrlOptions options)
{
var fileName = GetFileName(attachment);
var builder = new StringBuilder().AppendFormat("~/getattachment/{0:D}/{1}", attachment.GUID, GetFileNameForUrl(fileName));
var referenceLength = builder.Length;
Action<string, object> append = (name, value) =>
{
builder.Append(builder.Length == referenceLength ? '?' : '&').Append(name).Append('=').Append(value);
};
if (constraint.WidthComponent > 0)
{
append("width", constraint.WidthComponent);
}
if (constraint.HeightComponent > 0)
{
append("height", constraint.HeightComponent);
}
if (constraint.MaxWidthOrHeightComponent > 0)
{
append("maxsidesize", constraint.MaxWidthOrHeightComponent);
}
// Prevent Kentico from using site settings
if (!constraint.IsEmpty)
{
append("resizemode", "force");
}
if ((options != null) && options.AttachmentContentDisposition)
{
append("disposition", "attachment");
}
var url = builder.ToString();
if (attachment.VersionID > 0)
{
url = GetAttachmentPreviewUrl(url);
}
return instance.Target.Content(url);
}