Question

我们目前正在为每个数据表构建一个具有基本CRUD功能的web api和控制器。我们遇到的问题是更新。我们创建了自定义绑定模型，仅引入我们需要的数据，然后将该绑定模型转换为对象，并将其传递给我们的更新函数。

我们遇到的问题是，当客户端通过POST发送数据时，我们的绑定模型接收它并填充它们使用值设置的字段，以及填充为null的所有其他内容。因此，当我们将其转换为数据对象并将其发送到Update函数时，它会覆盖从客户端设置为null的字段。

这显然会导致问题，因为我们不希望用户意外删除信息。

以下是我们如何使用客户端，绑定模型和更新来运行的示例

团队绑定模型

/// <summary>A Binding Model representing the essential elements of the Team table</summary>
public class TeamBindingModel
{
    /// <summary>The Id of the team</summary>
    [Required(ErrorMessage = "An ID is required")]
    public int ID { get; set; }

    /// <summary>The name of the team</summary>
    [Required(ErrorMessage = "A Team Name is required")]
    [Display(Name = "Team Name")]
    [StringLength(35)]
    public string Team1 { get; set; }

    /// <summary>The email associated with the team</summary>
    [StringLength(120)]
    [DataType(DataType.EmailAddress)]
    public string Email { get; set; }

    public bool ShowDDL { get; set; }
}

UpdateTeam CRUD方法

// PUT: api/Team
/// <summary>
/// Attempt to update a team with a given existing ID
/// </summary>
/// <param name="team">TeamBindingModel - The binding model which needs an Id and a Team name</param>
/// <returns>IHttpActionResult that formats as an HttpResponseCode string</returns>
[HttpPut]
[Authorize(Roles = "SystemAdmin.Teams.Update")]
public async Task<IHttpActionResult> UpdateTeam(TeamBindingModel team)
{
    if (!ModelState.IsValid)
    {
        return BadRequest(ModelState);
    }

    try
    {
        // Convert the binding model to the Data object
        Team teamObject = team.ToObject();

        unitOfWork.TeamRepository.Update(teamObject);
        await unitOfWork.Save();
    }
    catch (DbUpdateConcurrencyException)
    {
        return BadRequest();
    }
    catch (Exception ex)
    {
        return BadRequest(ex.Message);
    }

    return Ok();
}

ToObject功能

/// <summary>Takes the Team Binding model and converts it to a Team object</summary>
/// <returns>Team Object</returns>
public virtual Team ToObject()
{
    // Setup the data object
    Team newObject = new Team();

    // Instantiate the basic property fields
    newObject.ID = this.ID;
    newObject.Team1 = this.Team1;
    newObject.Email = this.Email;
    newObject.ShowDDL = this.ShowDDL;

    return newObject;
}

更新功能

public virtual void Update(TEntity entityToUpdate)
{
    try
    {
        dbSet.Attach(entityToUpdate);
        dbContext.Entry(entityToUpdate).State = EntityState.Modified;
    }
    catch (Exception ex)
    {
        throw ex;
    }
}

保存功能

public async Task Save()
{
    await dbContext.SaveChangesAsync();
}

客户电话/测试/错误

// Add team to update and remove
var db = new genericDatabase();
var teamDB = new Team { Team1 = "testTeam", Email = "test@email.com", ShowDDL = true};

db.Teams.Add(teamDB);
db.SaveChanges();

// Look for items in the database
var originalTeamInQuestion = (from b in db.Teams
                                where b.Team1 == "testTeam"
                                select b).FirstOrDefault();

// Create Team object with the some changes
var team = new
{
    ID = originalTeamInQuestion.ID,
    Team1 = "changedTestTeam",
    ShowDDL = false,
};

// This is the API call which sends a PUT with only the parameters from team
var teamToUpdate = team.PutToJObject(baseUrl + apiCall, userAccount.token);

// Look for items in the database
var changedTeamInQuestion = (from b in db.Teams
                                where b.Team1 == "changedTestTeam"
                                select b).FirstOrDefault();

// This Assert succeeds and shows that changes have taken place
Assert.AreEqual(team.Team1, changedTeamInQuestion.Team1);

// This Assert is failing since no Email information is being sent
// and the binding model assigns it to Null since it didn't get that 
// as part of the PUT and overrides the object on update.
Assert.AreEqual(originalTeamInQuestion.Email, changedTeamInQuestion.Email);

关于某些替代方法的任何想法？我们想过要求客户首先通过对API进行GET调用然后更改对象来获取整个对象，但如果客户端没有遵循该协议，他们可能会非常危险地消除敏感数据

Answer 1

我实现了一个静态类，它将获取enity对象并仅更新实体的脏属性。这允许最终用户在需要时将值显式设置为null。

public static class DirtyProperties
{
    public static T ToUpdatedObject<T>(T entityObject)
    {
        return UpdateObject(entityObject,GetDirtyProperties());
    }

    private static Dictionary<string,object>GetDirtyProperties()
    {
        //Inspects the JSON payload for properties explicitly set.
        return JsonConvert.DeserializeObject<Dictionary<string, object>>(new StreamReader(HttpContext.Current.Request.InputStream).ReadToEnd());
    }

    private static T UpdateObject<T>(T entityObject, Dictionary<string, object> properties)
    {

        //Loop through each changed properties and update the entity object with new values
        foreach (var prop in properties)
        {
            var updateProperty = entityObject.GetType().GetProperty(prop.Key);// Try and get property

            if (updateProperty != null)
            {
                SetValue(updateProperty, entityObject, prop.Value);
            }
        }

        return entityObject;
    }

    private static void SetValue(PropertyInfo property, object entity, object newValue)
    {
        //This method is used to convert binding model properties to entity properties and set the new value
        Type t = Nullable.GetUnderlyingType(property.PropertyType) ?? property.PropertyType;
        object safeVal = (newValue == null) ? null : Convert.ChangeType(newValue, t);

        property.SetValue(entity, safeVal);
    }
}

Web Api通过绑定模型仅更新特定属性

1 个答案: