linq-count

C# – Get dictionary key by value

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Dictionaries have keys mapped to values, which enables you to efficiently lookup values by key. But you can also do a reverse lookup: get the key associated with a value. The simplest option is to use FirstOrDefault(), but that’s only a good idea if you know the value exists for sure. Instead, the best option … Read more

C# – Get value from dictionary

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Dictionaries store key/value pairs. When you want to get the value for a key, you can use the indexer syntax and specify the key, like this: Note: In order to show how to get a value, I had to initialize the dictionary with key/value pairs. This returns the value associated with the “Bob” key and … Read more

C# – How to parse XML with XElement (Linq)

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Use the XElement class (from the Linq-to-Xml API) to parse XML and work with it in memory. You can use this to search for XML elements, attributes, and modify values. This is an alternative to using an XML (de)serializer (which requires you to define a class that matches the XML structure). I’ll show examples of … Read more

ASP.NET Core – Receive a request with CSV data

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There are two ways to receive CSV data in a web API: In this article, I’ll show examples of both of these approaches. I’ll be using the CsvHelper library to parse CSV data into model objects and then do model validation. Note: To use CsvHelper, install the CsvHelper package (Install-Package CsvHelper). Or use whichever parser … Read more

C# – Find XML element by name with XElement (Linq)

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Use the XElement class (from the Linq-to-Xml API) to search for XML elements by name. There are two main methods you can use to do this: These return the matching elements as an IEnumerable<XElement>. You can then use Linq methods (or a foreach loop) to do whatever you want with these elements (such as outputting … Read more

C# – How to check if a type has a default constructor

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A default constructor is a constructor that doesn’t have parameters. Therefore, to check if a type has a default constructor, you can use reflection to loop through the constructors and see if there are any with no parameters, like this: In this article I’ll show an example of loading types that implement a specific interface … Read more