Equals sign (=) added after valueless query string parameters

Question

When rendering an external link from a General Link field using the Glass Mapper BeginRenderLink helper, any query string parameters without values are getting an equals sign (=) added after them.

An example

The URL

http://website.com/page?param1&param2=very_yes

becomes

http://website.com/page?param1=&param2=very_yes

The view markup

<div class="button">
    @using (BeginRenderLink(x => x.ButtonURL, new { @class = "button-highlight"}))
    {
        @Model.ButtonText
    }
</div>

For most systems, the difference between a query string parameter having an empty value and no value does not impact the functionality. In our case, however, we're linking to a system that throws an error if the value exists but is empty. Is there a way to fix this issue?

Answer 1

This issue is caused by how Glass Mapper generates URLs with its UrlBuilder:

public override string ToString()
{
    StringBuilder sb = new StringBuilder();

    // [get the first part of the URL] (omitted for brevity)

    foreach (var keyValuePair in QueryString)
    {
        if (keyValuePair.Key.HasValue())
        {
            sb.AppendFormat("{0}={1}{2}", keyValuePair.Key ?? string.Empty, keyValuePair.Value ?? string.Empty,QuerySeparator);
        }
    }

    // [remove the last separator] (omitted for brevity)

    return sb.ToString();
}

Note the line where it appends the next query string parameter concatenated with an = and its value, even if the value is empty.

The fix

I didn't want to change this functionality in Glass Mapper, because I figured it was actually MORE likely to be what people want. But for our case I needed a solution, so here's what I came up with:

Create a custom GlassHtml utility

Override the default BeginRenderLink behavior by replacing any offending contents of the generated URL.

public class CustomGlassHtml : GlassHtml
{
    public CustomGlassHtml(ISitecoreContext sitecoreContext) : base(sitecoreContext)
    {
    }

    public override RenderingResult BeginRenderLink<T>(T model, Expression<Func<T, object>> field, TextWriter writer, object parameters = null, bool isEditable = false, bool alwaysRender = false)
    {
        // We use a StringWriter to capture the rendering output from Glass so we can 
        // prevent the case where Glass' UrlBuilder adds a = after a valueless parameter.
        // For example:
        //   http://website.com/page?param1&param2=very_yes
        //   becomes
        //   http://website.com/page?param1=&param2=very_yes

        var glassRenderedLink = new StringBuilder();
        var stringWriter = new StringWriter(glassRenderedLink);

        // Call the standard BeginRenderLink. When the RenderingResult is created, it immediately writes the "first part" to the passed in writer
        RenderingResult renderingResult = base.BeginRenderLink(model, field, stringWriter, parameters, isEditable, alwaysRender);
        string firstPart = glassRenderedLink.ToString();
        glassRenderedLink.Clear();

        // When the RenderingResult is disposed, it writes the "last part" to its writer
        renderingResult.Dispose();
        string lastPart = glassRenderedLink.ToString();

        // Then we fix the URL problem
        firstPart = firstPart.Replace("=&", "&");

        // And return our own RenderingResult
        return new RenderingResult(writer, firstPart, lastPart);
    }
}

Create a custom GlassHtmlFactory to return your CustomGlassHtml

public class CustomGlassHtmlFactory : IGlassHtmlFactory
{
    public IGlassHtml GetGlassHtml(ISitecoreContext sitecoreContext)
    {
        return new CustomGlassHtml(sitecoreContext);
    }
}

Set your CustomGlassHtmlFactory as the GlassHtmlFactory in the GlassMapperScCustom class

public static IDependencyResolver CreateResolver()
{
    var config = new Glass.Mapper.Sc.Config();

    var dependencyResolver = new DependencyResolver(config);
    // add any changes to the standard resolver here

    // Register our custom GlassHtml class
    dependencyResolver.GlassHtmlFactory = new CustomGlassHtmlFactory();

    dependencyResolver.Finalise();

    return dependencyResolver;
}