使用C#创建Firebase规则时出现System.NullReferenceException如何修复？

我为Firebase规则服务创建了认证函数，并调用服务实例来创建Firebase规则集，但返回错误：System.NullReferenceException: Object reference not set to an instance of an object。拆分对象后，空引用异常出现在创建Source实例的代码行。

原始代码 #

using Google.Apis.FirebaseRules.v1;
using Ruleset = Google.Apis.FirebaseRules.v1.Data.Ruleset;
using Source = Google.Apis.FirebaseRules.v1.Data.Source;
using File = Google.Apis.FirebaseRules.v1.Data.File;

private static FirebaseRulesService _firebaseRulesService;


public static void IntializeFirebaseRules() {
    GoogleCredential credential = GoogleCredential.GetApplicationDefault();
    if (CloudManager.Credential.IsCreateScopedRequired)
    {
        credential = CloudManager.Credential.CreateScoped(FirebaseRulesService.Scope.CloudPlatform);
    }
    _firebaseRulesService = new FirebaseRulesService(
    new BaseClientService.Initializer()
        {
            HttpClientInitializer = credential,
            ApplicationName = CloudManager.ApplicationName

        });
}
    

 public static async  void AddRuleset()
{
    Ruleset myRuleset = new Ruleset {
    new Source {
        Files = {
        new File {
        Name = "firestore.rules",
        Content = "service cloud.firestore {" +
        "match /databases/{database}/documents {" +
        "match /users/{userId}{" +
        "allow read: if (request.auth.uid == userId);" +
        "}" +
        "match /licenses/{accountId} {" +
        "allow read: if isAccountOwner(accountId);" +
        "}" +
        "}"+"}",
            }
            }
        };
    };


    _firebaseRulesService.Projects.Rulesets.Create(myRuleset , "projects/" + CloudManager.ProjectId);
}

修改后的代码（异常出现在Source实例创建行） #

File myFile =  new File {
    Name = "firestore.rules",
    Content = "service cloud.firestore {" +
    "match /databases/{database}/documents {" +
    "match /users/{userId}{" +
    "allow read: if (request.auth.uid == userId);" +
    "}" +
    "function doc(subpath) {" +
    "return get(/databases/$(database)/documents/$(subpath)).data;" +
    "}" +
    "function isAccountOwner(accountId) {" +
    "return request.auth.uid == accountId" + 
    "|| doc(/users/$(request.auth.uid)).accountId == accountId;" +
    "}" +
    "match /licenses/{accountId} {" +
    "allow read: if isAccountOwner(accountId);" +
    "}" +
    "}"+"}",
};
Source mySource = new Source {
    Files = {
        myFile
    }  
};
Ruleset myRuleset = new Ruleset {
    Source = mySource
};

_firebaseRulesService.Projects.Rulesets.Create(myRuleset , "projects/" + CloudManager.ProjectId);

空引用异常的核心原因是**Source类的Files集合未被初始化**。在C#中使用集合初始化语法（Files = { myFile }）时，要求集合本身已经被实例化，否则会触发空引用错误。

具体修复步骤： #

1. 显式初始化Files集合
   创建Source实例时，先将Files初始化为新的List<File>实例，再添加文件对象：

   Source mySource = new Source {
       Files = new List<File> { myFile }
   };
   

2. 排查其他潜在空引用点

   • 确保_firebaseRulesService已通过IntializeFirebaseRules()方法正确初始化，避免调用Create接口时服务实例为空。
   • 验证CloudManager.ProjectId不为空或空字符串，保证请求的项目ID合法有效。

3. 修正原始代码的语法错误
   原始代码中Ruleset初始化器存在语法错误，直接嵌套new Source不符合C#对象初始化规则，正确写法应为给Ruleset的Source属性赋值：

   Ruleset myRuleset = new Ruleset {
       Source = new Source {
           Files = new List<File> {
               new File {
                   Name = "firestore.rules",
                   Content = "// 规则内容..."
               }
           }
       }
   };
   

4. 规范异步方法写法
   AddRuleset声明为async void仅适用于事件处理程序，建议改为async Task以支持异步等待和错误捕获，同时调用ExecuteAsync()执行异步请求：

   public static async Task AddRuleset()
   {
       // 代码逻辑...
       await _firebaseRulesService.Projects.Rulesets.Create(myRuleset, "projects/" + CloudManager.ProjectId).ExecuteAsync();
   }
   

内容的提问来源于stack exchange，提问作者Samaritan