获取token时如何解析"possible System.NullReferenceException"

Question

我正在按照 "Azure-Sample" 中提供的示例代码获取令牌以调用 Microsoft Graph Api。但是 Resharper 建议 "Possible System.NullReferenceException" in await app.AcquireTokenForClient(scopes) .ExecuteAsync();如何解决 NullReference 异常？

克隆代码并查看 "Possible System.NullReferenceException"

AuthenticationResult result = null;
            try
            {
                result = await app.AcquireTokenForClient(scopes)
                    .ExecuteAsync();
                Console.ForegroundColor = ConsoleColor.Green;
                Console.WriteLine("Token acquired");
                Console.ResetColor();
            }
            catch (MsalServiceException ex) when (ex.Message.Contains("AADSTS70011"))
            {
                // Invalid scope. The scope has to be of the form "https://resourceurl/.default"
                // Mitigation: change the scope to be as expected
                Console.ForegroundColor = ConsoleColor.Red;
                Console.WriteLine("Scope provided is not supported");
                Console.ResetColor();
            }

Resharper 建议 "Possible System.NullReferenceException"，知道如何解决吗？

Answer 1

处理这种情况的方法是检查是否为空，如果是则引发异常。

假设 app 是您的方法的输入变量：

void Foo(IApp app) //just using IApp as an example.
{
    if (app == null)
        throw new ArgumentNullException(nameof(app));

    var result = app.Bar(); //no possible null ref here.
}

Answer 2

"Pessimistic" 值分析模式在 ReSharper 中启用，它认为一切都可以是 "null"，除非明确检查是否为 null 或使用 "NotNull" 或 "ContractAnnotation" 属性进行注释. 处理这种情况的一些选项：

为 "AcquireTokenForClient"
将"app.AcquireTokenForClientAsync(scopes)"提取到局部变量并检查它是否为空：

var task = app.AcquireTokenForClientAsync(作用域); 如果（任务== null）抛出新的异常（）；结果=等待任务；
启用"Optimistic"值分析模式

获取token时如何解析"possible System.NullReferenceException"

How to resolve "possible System.NullReferenceException" while acquiring token

c#

azure

azure-active-directory

resharper

msal