Throw Exceptions Contract

Aug 03, 2020
2 minutes to read

Purpose

This Code Provider adds the guard precondition to method parameter(s) or a variable assignment. The precondition ensures the passed or assigned values are not empty and throws the ArgumentException (or ArgumentNullException) in case they are.

Availability

Available in the following cases.

When the caret is at the beginning of a method body. In this case, the contract will test all method parameters and strings.
When the caret is on a method’s parameter name. In this case, the contract will test only the selected parameter.
When the caret is on a variable assignment.

Note

This Code Provider may be unavailable for variables of a non-nullable type, for instance, Integer.

Usage

Place the caret at the beginning of a method body.
Press the Ctrl + . or Ctrl + ~ shortcut to invoke the Code Actions menu.
Select Add Contract | Throw Exceptions Contract from the menu.

After execution, the Code Provider adds the guard conditional against all the method parameters.

C#
VB.NET

csharp

public bool AddRecord(string name, object data) {
    if (string.IsNullOrEmpty(name))
        throw new ArgumentException($"{nameof(name)} is null or empty.", nameof(name));
    if (data == null)
        throw new ArgumentNullException(nameof(data), $"{nameof(data)} is null.");

    //...
    return true;
}

Public Function AddRecord(ByVal name As String, ByVal data As Object) As Boolean
    If String.IsNullOrEmpty(name) Then
        Throw New ArgumentException($"{NameOf(name)} is nothing or empty.", NameOf(name))
    End If

    If data Is Nothing Then
        Throw New ArgumentNullException(NameOf(data), $"{NameOf(data)} is nothing.")
    End If

    '... 
    Return True
End Function

You can ask CodeRush to check arrays and collections length in code contracts. Refer to the Code Actions Settings topic for more information.