dotnet/maui · error · ArgumentNullException

The parameter cannot be either null or empty.

Error message

The parameter cannot be either null or empty.

What it means

Verify.IsNeitherNullNorEmpty is an argument-validation helper that throws ArgumentNullException when the supplied string value is null. It is intended as a guard clause at the top of public methods. The paramName is taken from the 'name' argument so the exception points at the offending parameter.

Source

Thrown at src/Compatibility/Core/src/WPF/Microsoft.Windows.Shell/Standard/Verify.cs:62

		/// <summary>
		/// Ensure that an argument is neither null nor empty.
		/// </summary>
		/// <param name="value">The string to validate.</param>
		/// <param name="name">The name of the parameter that will be presented if an exception is thrown.</param>
		[SuppressMessage("Microsoft.Performance", "CA1811:AvoidUncalledPrivateCode")]
		[SuppressMessage("Microsoft.Performance", "CA1820:TestForEmptyStringsUsingStringLength")]
		[DebuggerStepThrough]
		public static void IsNeitherNullNorEmpty(string value, string name)
		{
			// catch caller errors, mixing up the parameters.  Name should never be empty.
			Assert.IsNeitherNullNorEmpty(name);

			// Notice that ArgumentNullException and ArgumentException take the parameters in opposite order :P
			const string errorMessage = "The parameter cannot be either null or empty.";
			if (null == value)
			{
				Assert.Fail();
				throw new ArgumentNullException(name, errorMessage);
			}
			if ("" == value)
			{
				Assert.Fail();
				throw new ArgumentException(errorMessage, name);
			}
		}

		/// <summary>
		/// Ensure that an argument is neither null nor does it consist only of whitespace.
		/// </summary>
		/// <param name="value">The string to validate.</param>
		/// <param name="name">The name of the parameter that will be presented if an exception is thrown.</param>
		[SuppressMessage("Microsoft.Performance", "CA1811:AvoidUncalledPrivateCode")]
		[SuppressMessage("Microsoft.Performance", "CA1820:TestForEmptyStringsUsingStringLength")]
		[DebuggerStepThrough]
		public static void IsNeitherNullNorWhitespace(string value, string name)
		{

View on GitHub (pinned to f377ff1c5e)

Solutions

1. Pass a non-null, non-empty string — initialize the value before calling the API.
2. Guard at the call site with a null check and a meaningful default or early return.
3. Use nameof(parameter) so the exception message names the correct parameter.

Example fix

// before
DoWork(path); // path may be null

// after
if (path == null) throw new ArgumentNullException(nameof(path));
DoWork(path);

// Pre-check for null before calling the guarded API
if (value == null)
{
    throw new ArgumentNullException(nameof(value));
}
SomeApi(value);

When it happens

Trigger: Calling a public method whose first lines run Verify.IsNeitherNullNorEmpty(value, nameof(value)) and passing null for value. The Assert.Fail() that precedes the throw only fires in debug builds; the exception always throws.

Common situations: Caller omitted a required string argument; a property backing field was never initialized; a config or path string came back null from a lookup and was forwarded without a null check.

Related errors

• The parameter cannot be either null or empty or consist only
• The parameter must not be the default value.
• The parameter must be null.
• The URI must be absolute.
• The integer value must be bounded with [{0}, {1})

AI-assisted analysis of dotnet/maui@f377ff1c5e (2026-08-13). Data as JSON: /api/errors/5825c779b5f989c2. Report an issue: GitHub.