IsNullOrEmpty(string) and List.Count > 0 in mustache-sharp

Question

I use mustache-sharp as template engine

I want to know Is there anyway by using this template engine and have two conditions for checking

1) IsNullOrEmpty(string)  => e.g. {{#IsNullOrEmpty MyName}}} {{/IsNullOrEmpty}}
2) List.Count > 0         => e.g. {{#Any Persons}} {{/Any}}

Can anyone guide me How can I create tags like above ?

Answer 1

You can try to create a custom ContentTagDefinition and register it in HtmlFormatCompiler.

For example:

1. IsNullOrEmpty

   public class IsNullOrEmptyTagDefinition : ContentTagDefinition
   {
       private const string conditionParameter = "condition";
   
       public IsNullOrEmptyTagDefinition()
           : base("IsNullOrEmpty")
       {}
   
       public override IEnumerable<TagParameter> GetChildContextParameters()
       {
           return new TagParameter[0];
       }
   
       public override bool ShouldGeneratePrimaryGroup(Dictionary<string, object> arguments)
       {
           object condition = arguments[conditionParameter];
           return isConditionSatisfied(condition);
       }
   
       protected override IEnumerable<TagParameter> GetParameters()
       {
           return new TagParameter[] { new TagParameter(conditionParameter) { IsRequired = true } };
       }
   
       protected override bool GetIsContextSensitive()
       {
           return false;
       }
   
       private bool isConditionSatisfied(object condition)
       {
           if (condition == null)
           {
               return true;
           }
   
           return condition is string ? string.IsNullOrEmpty(condition as string) : false;
       }
   
   }
   

2. Any

   public class AnyTagDefinition : ContentTagDefinition
   {
       private const string conditionParameter = "condition";
   
       public AnyTagDefinition()
           : base("Any")
       {}
   
       public override IEnumerable<TagParameter> GetChildContextParameters()
       {
           return new TagParameter[0];
       }
   
       public override bool ShouldGeneratePrimaryGroup(Dictionary<string, object> arguments)
       {
           object condition = arguments[conditionParameter];
           return isConditionSatisfied(condition);
       }
   
       protected override IEnumerable<TagParameter> GetParameters()
       {
           return new TagParameter[] { new TagParameter(conditionParameter) { IsRequired = true } };
       }
   
       protected override bool GetIsContextSensitive()
       {
           return false;
       }
   
       private bool isConditionSatisfied(object condition)
       {
           if (condition is IEnumerable)
           {
               return (condition as IEnumerable).Cast<object>().Any();
           }
   
           return false;
       }
   
   }
   

3. Register both tags

   HtmlFormatCompiler compiler = new HtmlFormatCompiler();
   compiler.RegisterTag(new IsNullOrEmptyTagDefinition(), true);
   compiler.RegisterTag(new AnyTagDefinition(), true);