小编Ben*_*Ben的帖子

我在简单的Android应用程序中写入Firebase数据库时遇到问题.我已将数据库规则设置为公开:

{
  "rules": {
    ".read": true,
    ".write": true
  }
}

创建了一个简单的类Message:

import com.google.firebase.database.DatabaseReference;
import com.google.firebase.database.FirebaseDatabase;

public class Message {
    FirebaseDatabase database = FirebaseDatabase.getInstance();
    DatabaseReference dbRef = database.getReference();
    public String sender;
    public String message;

    public Message(){}

    public Message(String sender, String message) {
        this.sender = sender;
        this.message = message;
    }
}

并设置一个按钮来执行onClick方法writeNewMessage,这些方法是重要的代码行:

int counter = 0;

public void writeNewMessage(View view) {

        counter += 1;
        Message messageToWrite = new Message("John", "Simple message: " + counter);
        String messageId = String.valueOf(counter); …

当模型在我的 Web API 项目中验证失败时，我试图返回自定义响应对象。我已将属性附加到模型中，如下所示：

  public class DateLessThanAttribute : ValidationAttribute
  {
    private readonly string _comparisonProperty;

    public DateLessThanAttribute(string comparisonProperty)
    {
      _comparisonProperty = comparisonProperty;
    }

    protected override ValidationResult IsValid(object value, ValidationContext validationContext)
    {
      ErrorMessage = ErrorMessageString;
      var currentValue = (DateTime)value;

      var property = validationContext.ObjectType.GetProperty(_comparisonProperty);

      if (property == null)
        throw new ArgumentException("Property with this name not found");

      var comparisonValue = (DateTime)property.GetValue(validationContext.ObjectInstance);

      if (currentValue > comparisonValue)
        return new ValidationResult(ErrorMessage);

      return ValidationResult.Success;
    }
  }

在模型上：

[DateLessThan("EndDate", ErrorMessage = "StartDate must be less than EndDate")]
public DateTime …