argumentnullexception

C# – Convert string list to int list

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You can convert a list of strings to a list of integers by using int.Parse() on all of the strings. There are two simple ways to do this: I’ll show examples of these using these methods and then explain how to handle parsing exceptions. Option 1 – Use List.ConvertAll() Here’s an example of how to … Read more

C# – Suppress nullable warnings (CS8602)

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Sometimes the compiler shows unhelpful nullable warnings. Here’s an example of it showing warning CS8602, when it’s obvious to any human reading the code that you’re doing a null-check already (in ThrowIfNull()): Besides disabling the Nullable feature, there are two ways to suppress nullable warnings on a case-by-case basis: I’ll show both options below. Option … Read more

CA2208: Instantiate argument exceptions correctly

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The CA2208 code analysis rule checks for common mistakes when constructing argument exceptions. There are three main argument exception classes: ArgumentException, ArgumentNullException, and ArgumentOutOfRangeException. Unfortunately, it’s easy to make a mistake when using these. I’ll explain the common mistakes that CA2208 checks for and how to fix them (and when to suppress the warning instead). … Read more

C# – Get argument names automatically

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You can use the CallerArgumentExpression attribute to automatically get the name of an argument being passed into a method: Note: CallerArgumentExpression was added in .NET 6. Here’s an example to show what CallerArgumentExpression does: Calling this method outputs the following: You use the CallerArgumentExpression attribute with a default string parameter (i.e. string argumentName = null). … Read more

C# – Hide a method from the stack trace

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When you want to exclude a method from showing up in the stack trace, you can apply the StackTraceHidden attribute to the method: Note: This attribute was added in .NET 6. You can apply StackTraceHidden to a class to hide all of its methods from the stack trace: Use StackTraceHidden with throw helper methods StackTraceHidden … Read more

C# – The nameof() operator

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The nameof() operator outputs the name of the class/method/property/type passed into it. Here’s an example: Note: nameof() was added in C# 6. nameof() eliminates duplication The DRY principle – Don’t Repeat Yourself – warns us against having duplication in the code. Whenever information or code is duplicated, it’s possible to change something in one spot … Read more

CA1062: Validate parameter is non-null before using it

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When you have a public method that isn’t null checking its parameters, then you’ll get the CA1062 code analysis warning. This is part of the Nullable Reference Types feature. For example, the following code isn’t null checking the movieRepository parameter: This results in the CA1062 code analysis warning: CA1062 In externally visible method ‘void StreamingService.LogMovies(MovieRepository … Read more

C# – Merge two dictionaries in-place

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When you merge two dictionaries, you can either merge them in-place, or create a new dictionary and copy the values over to it. The following extension method does an in-place merge of two dictionaries. It loops through items in the right dictionary, adding them to the left dictionary. When duplicate keys exist, it’s keeping the … Read more