AutoCompleteSuggestHelper, Assembly: Telerik.WinControls.UI, Version=2019.1.117.40

 

Isnt the hilighted line (contains branch) very unoptimized.

https://rhale78.wordpress.com/2011/05/16/string-equality-and-performance-in-c/

Multiple ToLower string operation. Why not let the framework do the operation since you are always using ordinal?

optimized version: return item.Text.Contains(this.Filter, StringComparison.OrdinalIgnoreCase);

 

protected virtual bool DefaultFilter(RadListDataItem item)
    {
      switch (this.suggestMode)
      {
        case SuggestMode.StartWiths:
          return item.Text.StartsWith(this.Filter, this.StringComparison);
        case SuggestMode.Contains:
          if ((this.StringComparison & StringComparison.InvariantCultureIgnoreCase) == StringComparison.InvariantCultureIgnoreCase || (this.StringComparison & StringComparison.InvariantCultureIgnoreCase) == StringComparison.CurrentCultureIgnoreCase)
            return item.Text.ToLower().Contains(this.Filter.ToLower());
          return item.Text.Contains(this.Filter);
        default:
          return item.Text.StartsWith(this.Filter, this.StringComparison);
      }
    }