Css Builder Extensions

BuilderUsage.cshtml

<li aria-selected=@IsActive role="tab" class="@ClassToRender">
  ...
</li>

@functions {
  ...
  protected bool IsActive => ContainerTabSet.ActiveTab == this;
  [Parameter] protected bool Disabled { get; set; }
  [Parameter] protected string Class { get; set; }

  protected string ClassToRender { get; set; }

  protected override void OnParametersSet()
  {        
    ClassToRender = new CssBuilder(Class) // User supplied CSS
                          .AddClass("tab-item") // base CSS
                          .AddClass("tab-state-active tab-tab-on-top", IsActive)
                          .AddClass("tab-state-default", !IsActive)
                          .AddClass("tab-state-disabled", Disabled)
                          .Build();
        }
}

CssBuilder.cs

public class CssBuilder
{
    private readonly StringBuilder sb;
    public CssBuilder() => sb = new StringBuilder();
    public CssBuilder(string value) => sb = new StringBuilder(value);

    public CssBuilder AddValue(string value) 
    {
        sb.Append(value);
        return this;
    }

    public CssBuilder AddClass(string value) => AddValue(" ").AddValue(value);
    public CssBuilder AddClass(string value, bool when = true) => condition ? this.AddClass(value) : this;
    public CssBuilder AddClass(string value, Func<bool> when = null) => this.AddClass(value, when());
    public string Build() => ToString();
    public override string ToString() => sb.ToString();

}

CssExtensions.cs

    static class CssExtensions
    {
        public static StringBuilder AppendCss(this StringBuilder sb, string value) => sb.Append(" ").Append(value);
        public static StringBuilder AppendCssWhen(this StringBuilder sb, string value, bool condition) => condition ? sb.AppendCss(value) : sb;
        public static StringBuilder AppendCssWhen(this StringBuilder sb, string value, Func<bool> condition) => condition() ? sb.AppendCss(value) : sb;
        public static string ToCssString(this StringBuilder sb) => sb.ToString().Trim();
    }
    
    

usage.cshtml

<li aria-selected=@IsActive role="tab" class="@ClassToRender">
  ...
</li>

@functions {
  ...
  protected bool IsActive => ContainerTabSet.ActiveTab == this;
  [Parameter] protected bool Disabled { get; set; }
  [Parameter] protected string Class { get; set; }

  protected string ClassToRender { get; set; }

  protected override void OnParametersSet()
  {
       ClassToRender = new StringBuilder(Class) // User supplied CSS
                             .AppendCss("tab-item") // Base CSS
                             .AppendCssWhen("tab-state--active tab-on-top", IsActive)
                             .AppendCssWhen("tab-state--default", !IsActive)
                             .AppendCssWhen("tab-state--disabled", Disabled)
                             .ToCssString();
  }
}