C# – Search XML for elements, values, and attributes

The simplest way to search XML is to use the Linq-to-XML API in .NET (in System.Xml.Linq). This parses XML and allows you to perform Linq queries on it. Here’s an example: This outputs: XElement is the main class. You use it in combination with Linq methods to perform searches. In this article, I’ll how to … Read more

System.InvalidOperationException: Sequence contains no elements

Problem When you call .First() on an empty IEnumerable, you get the following exception: System.InvalidOperationException: Sequence contains no elements Solution Option 1 – Use .FirstOrDefault() instead of .First() When the IEnumerable is empty, .FirstOrDefault() returns the default value for the type. For reference types this returns null. For value types this returns 0 or that … Read more

WinForms: How to check if another form is open

If you’re working on a Windows Forms project and need to know which forms are open, use: This gives you an IEnumerable collection of form objects that are currently open. You can lookup a form by name, by type, or loop through the list. Example scenarios There are many scenarios where you’d want to know … Read more