c# - 使用 ViewModel 从多个表中获取数据？

Question

我有 3 个类用于规则、请求、执行和批准者。

我想将这三个表合并到一个 viewModel 中，这样我就可以在一个 View 中获取请求 ID、描述、批准者和执行状态。这是我第一次粗略的尝试，它似乎有效，但我觉得这是创建 ViewModel 的非常不正确的方法。请提出更好的方法。

public class Rules
{
    [Required]
    public virtual int RulesId { get; set; }
    [Required]
    public virtual string RulesDescription { get; set; }
    [Required]
    public virtual int ApprovalLevels { get; set; } //if 0 then auto approved.
    [Required]
    public virtual string Requestor { get; set; }
}

public class Requests
{
    [Required]
    public virtual int RequestsId { get; set; }
    [Required]
    public virtual DateTime RequestTime { get; set; }
    [Required]
    public virtual bool isCompleted { get; set; }
    [Required]
    public virtual string UserName { get; set; }
    [Required]
    public virtual int RulesId { get; set; }
    public virtual string Description { get; set; }
}

public class ExecutionStatus
{   
    [Required]
    public virtual int ExecutionStatusId { get; set; }
    [Required]
    public virtual int RequestId { get; set; }
    [Required]
    public virtual int CurrentApproverLevel { get; set; } 
    [Required]
    public virtual string ApprovalStatus { get; set; }
}
public class Approvals
{
    [Required]
    public virtual int ApprovalsId { get; set; }
    [Required]
    public virtual int RulesId { get; set; }
    [Required]
    public virtual int ApproverLevel { get; set; }
    [Required]
    public virtual string ApproverName { get; set; }
}



public class RequestExecutionViewModel
{
    private RequestsContext db = new RequestsContext();
    public RequestExecutionViewModel(string username) 
    {
          this.Request = db.Requests.Where(a => a.UserName.Equals(username)).First();
          //aa = db.Approvals.Where(a => a.RulesId.Equals(Request.RulesId));
          this.Approvals = (List<Approvals>) db.Approvals.Where(a => a.RulesId.Equals(Request.RulesId)).ToList();
          this.ExecutionStatus = (List<ExecutionStatus>)db.ExecutionStatus.Where(a => a.RequestId.Equals(Request.RequestsId)).ToList();
    }

    [Required]
    public virtual int RequestExecutionViewModelId { get; set; }
    public Requests Request   {get;set;}
    public List<Approvals> Approvals { get; set; }
    public List<ExecutionStatus> ExecutionStatus { get; set; }
}

编辑:在模型内部进行数据库查询对我来说似乎是错误的。应该有更好的做事方式。

Answer 1

组成相当不错，但是，你不应该private RequestsContext db = new RequestsContext();和 RequestExecutionViewModel()包含在 View 模型中。另外，您可能想使用 IList<>而不是 List<> .

您的数据库访问应该在服务层或 Controller 操作中执行，并且可能应该通过一些 IOC 容器注入(inject)。

只是我的 2 美分