In ASP.net we run into an issue when it comes our User Controls and their corresponding CSS loading in the main CSS files even when that User Control is not included in the 90% of the pages a user calls. (this is the same with JavaScript files)
In order to make sure that my User Control’s CSS is not unnecessarily loaded in the application’s main CSS file and to maintain a little more order in my design I like to use a little programming magic. This magic allows me to only load the CSS for a User Control when it is included in a page or another User Control.
To accomplish this magic I create a Base User Control from which all my User Controls inherit. This base control contains a method called LoadResources which does the following:
(All of the above are based on the CSS and JavaScript files having the same name as the control and those files being located in the same location as the current control.)
public class BaseUserControl : UserControl
{
#region Private Fields
private string _controlName;
#endregion
#region Protected Methods
///
/// Used if the control has custom CSS or Javascript
/// which needs to be loaded with the control.
/// The resources consist of a .css and .js files
/// which have the same name as the control. This method
/// will search the control's location for those 2
/// files and add them as CSS and Javascript links to
/// the control's ascx content.
///
protected void LoadResources()
{
PullControlName();
LoadCssFile();
LoadJsFile();
}
///
/// Loads the resources.
///
/// Name of the file.
/// Type of the file.
protected void LoadResources(string fileName, FileType fileType)
{
switch (fileType)
{
case FileType.Script:
LoadJsFile(fileName);
break;
case FileType.Style:
LoadCssFile(fileName);
break;
}
}
///
/// Loads the resources.
///
///
styleFileName">Name of the style file.
///
scriptFileName">Name of the script file.
protected void LoadResources(string styleFileName, string scriptFileName)
{
LoadCssFile(styleFileName);
LoadJsFile(scriptFileName);
}
#endregion
#region Private Methods
private void PullControlName()
{
string controlType = GetType().ToString();
List<string> controlParts = controlType.Split('_').ToList();
if (controlParts.Count > 0)
{
if (!string.IsNullOrEmpty(controlParts[controlParts.Count - 2]))
{
_controlName = controlParts[controlParts.Count - 2];
}
}
}
private void LoadCssFile()
{
try
{
// Injects the CSS for this control into the page header
string cssUrl = ResolveUrl(_controlName + ".css");
string cssPath = cssUrl.Remove(0, 1).Replace('/', '\\');
if (File.Exists(Request.PhysicalApplicationPath + cssPath))
{
string controlId = _controlName + "Style";
if (!DoesControlExist(controlId))
{
HtmlLink css = new HtmlLink();
css.ID = controlId;
css.Href = cssUrl;
css.Attributes.Add("rel", "stylesheet");
css.Attributes.Add("type", "text/css");
Page.Header.Controls.Add(css);
}
}
}
catch (Exception ex)
{
//TODO: Handle exception as a warning
}
}
private void LoadCssFile(string fileName)
{
try
{
// Injects the CSS for this control into the page header
string cssUrl = ResolveUrl(fileName);
string cssPath = cssUrl.Remove(0, 1).Replace('/', '\\');
if (File.Exists(Request.PhysicalApplicationPath + cssPath))
{
string controlId = fileName + "Style";
if (!DoesControlExist(controlId))
{
HtmlLink css = new HtmlLink();
css.ID = controlId;
css.Href = cssUrl;
css.Attributes.Add("rel", "stylesheet");
css.Attributes.Add("type", "text/css");
Page.Header.Controls.Add(css);
}
}
}
catch (Exception ex)
{
//TODO: Handle exception as a warning
}
}
private void LoadJsFile()
{
try
{
// Injects the JavaScript for this control into the page header
string jsUrl = ResolveUrl(_controlName + ".js");
string jsPath = jsUrl.Remove(0, 1).Replace('/', '\\');
if (File.Exists(Request.PhysicalApplicationPath + jsPath))
{
string controlId = _controlName + "Script";
if (!DoesControlExist(controlId))
{
HtmlGenericControl js = new HtmlGenericControl("script");
js.ID = controlId;
js.Attributes.Add("type", "text/javascript");
js.Attributes.Add("src", jsUrl);
Page.Header.Controls.Add(js);
}
}
}
catch (Exception ex)
{
//TODO: Handle exception as a warning
}
}
private void LoadJsFile(string fileName)
{
try
{
// Injects the JavaScript for this control into the page header
string jsUrl = ResolveUrl(fileName);
string jsPath = jsUrl.Remove(0, 1).Replace('/', '\\');
if (File.Exists(Request.PhysicalApplicationPath + jsPath))
{
string controlId = fileName + "Script";
if (!DoesControlExist(controlId))
{
HtmlGenericControl js = new HtmlGenericControl("script");
js.ID = controlId;
js.Attributes.Add("type", "text/javascript");
js.Attributes.Add("src", jsUrl);
Page.Header.Controls.Add(js);
}
}
}
catch (Exception ex)
{
//TODO: Handle exception as a warning
}
}
private bool DoesControlExist(string controlId)
{
object control = Page.Header.FindControl(controlId);
if (control != null)
return true;
return false;
}
#endregion
#region Utility Classes
///
/// Types of files which are accepted by the
/// resource loader.
///
public enum FileType
{
///
/// Cascading Style Sheet files
///
Style,
///
/// JavaScript files
///
Script
}
#endregion
}
