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c#asp.nettagbuilder

Can you control the order in which the TagBuilder class renders attributes?


I know this is kind of obsessive, but is there a way to control the order that the TagBuilder class renders the attributes of an HTML tag when you call ToString()?

i.e. so that

var tb = new TagBuilder("meta");            
tb.Attributes.Add("http-equiv", "Content-Type");            
tb.Attributes.Add("content", "text/html; charset=utf-8");    
tb.ToString(TagRenderMode.SelfClosing)

will return

<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />

not

<meta content="text/html; charset=utf-8" http-equiv="Content-Type" />

Changing the order that you add the attributes doesn't change it, it seems to be rendering in alphabetical order


Solution

  • Try using this class, which inherits the TagBuilder and overrides the ToString method, building a SortedDictionary from the Attributes and using that dictionary to render.

        public class MyTagBuilder : TagBuilder
        {
            //required to inherit from TagBuilder
            public MyTagBuilder(string tagName) : base(tagName){}
    
            //new hides the original ToString(TagRenderMode renderMode) 
            //The only changes in this method is that all calls to GetAttributesString
            //have been changed to GetMyAttributesString 
            public new string ToString(TagRenderMode renderMode)
            {
                switch (renderMode)
                {
                    case TagRenderMode.StartTag:
                        return string.Format(CultureInfo.InvariantCulture, "<{0}{1}>", new object[] { this.TagName, this.GetMyAttributesString() });
    
                    case TagRenderMode.EndTag:
                        return string.Format(CultureInfo.InvariantCulture, "</{0}>", new object[] { this.TagName });
    
                    case TagRenderMode.SelfClosing:
                        return string.Format(CultureInfo.InvariantCulture, "<{0}{1} />", new object[] { this.TagName, this.GetMyAttributesString() });
                }
                return string.Format(CultureInfo.InvariantCulture, "<{0}{1}>{2}</{0}>", new object[] { this.TagName, this.GetMyAttributesString(), this.InnerHtml });
            }
    
            //Implement GetMyAttributesString where the Attributes are changed to a SortedDictionary
            private string GetMyAttributesString()
            {
                var builder = new StringBuilder();
                var myDictionary = new SortedDictionary<string, string>();     //new
                foreach (KeyValuePair<string, string> pair in this.Attributes) //new
                {                                                              //new
                    myDictionary.Add(pair.Key, pair.Value);                    //new
                }                                                              //new 
                //foreach (KeyValuePair<string, string> pair in this.Attributes)
                foreach (KeyValuePair<string, string> pair in myDictionary)    //changed
                {
                    string key = pair.Key;
                    if (!string.Equals(key, "id", StringComparison.Ordinal) || !string.IsNullOrEmpty(pair.Value))
                    {
                        string str2 = HttpUtility.HtmlAttributeEncode(pair.Value);
                        builder.AppendFormat(CultureInfo.InvariantCulture, " {0}=\"{1}\"", new object[] { key, str2 });
                    }
                }
                return builder.ToString();
            }
        }