C# Nullable Annotation that method returns not null if parameter is not null

Question

如果输入不为空，我如何告诉编译器以下扩展方法 returns 不为空？

public static string? SomeMethod(this string? input)
{
    if (string.IsNullOrEmpty(input))
        return input;

    // Do some work on non-empty input
    return input.Replace(" ", "");
}

Answer 1

使用以下属性：

[return: NotNullIfNotNull("input")]
public static string? SomeMethod(this string? input)
{
   ...
}

进一步阅读：Attributes for null-state static analysis interpreted by the C# compiler

C# Nullable Annotation that method returns not null if parameter is not null

C# Nullable Annotation that method returns not null if parameter is not null

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nullable

nullable-reference-types