c# - 属性id是对象关键信息的一部分，不可修改

Question

当我尝试使用 EF 更新数据时，出现类似错误

the property id is part of the object's key information and cannot be modified

Thıs ıs wınForm 应用程序你可以在这里看到我的更新方法

区域更新

        try
        {
            _truck.plateNumber= txtplateNumber.Text;
            _truck.brand = txtMarka.Text;
            _truck.model = txtModel.Text;
            _truck.type = txtTipi.Text;
            _truck.registrationDate = dtregistrationDate.Value;
            _truck.examinationDate = dtexaminationDate.Value;
            _truck.Description = txtDescription.Text;
            _truck.driverName = txtdriverName.Text;
            _truck.weight= txtweight.Text;
            _truck.Id = Convert.ToInt32(txtplateNumber.Tag);
            _truck.userId = Tools.Tools.getUserId();

            #region update
            currentItem = cr.getbyId(Convert.ToInt32(txtplateNumber.Tag.ToString())).plateNumber;

            if (currentItem != null)
            {
                if (!currentItem.Equals(txtplateNumber.Text))
                {
                    if (!cr.isPlateAlreadyExist(txtplateNumber.Text))
                    {
                       DialogResult result = MessageBox.Show("Are you sure want to update to Truck?", "Update", MessageBoxButtons.YesNo, MessageBoxIcon.Question);
                        if (result == DialogResult.Yes)
                        {
                            if (!string.IsNullOrEmpty(this.pbLicence.ImageLocation))
                            {
                                _truck.licencePicture = Tools.Tools.convertToByteFfromImageF(pbLicence.Image);

                                if (!cr.getbyId(Convert.ToInt32(txtplateNumber.Tag)).hasPicture)
                                {
                                    _truck.hasPicture = true;
                                    cr.Update(_truck);
                                }
                            }

                            cr.Update(_truck);
                            MessageBox.Show("Successfuly");

                        }
                        else
                        {
                            MessageBox.Show("The process was Cancel !", "Canceled", MessageBoxButtons.OK, MessageBoxIcon.Information);
                        }
                    }
                    else
                    {
                        MessageBox.Show("The plate number is already Exists.", "Same Plate Number", MessageBoxButtons.OK, MessageBoxIcon.Stop);
                    }
                }
                else
                {
                    DialogResult result = MessageBox.Show("Are you sure want to update to Truck?", "Update", MessageBoxButtons.YesNo, MessageBoxIcon.Question);
                    if (result == DialogResult.Yes)
                    {
                        if (!string.IsNullOrEmpty(this.pbLicence.ImageLocation))
                        {
                            _truck.licencePicture = Tools.Tools.convertToByteFfromImageF(this.pbLicence.Image);

                            if (!cr.getbyId(Convert.ToInt32(txtplateNumber.Tag)).hasPicture)
                            {
                                _truck.hasPicture = true;
                                cr.Update(_truck);
                            }
                        }

                        cr.Update(_truck);
                        MessageBox.Show("SuccessFully");
                    }

                }
            #endregion
            }
            else
            {
                MessageBox.Show("You did not select an Item","Warning");
            }
        }
        catch (Exception ex)
        {
            MessageBox.Show("Error:" + ex.Message, "Error");
        }
        finally
        {
            getUpdatedList();
            Tools.Tools.clearAllFormControlsContent(pickTruckControls());
        }
        #endregion

------版本库更新方法------------

public int Update(Truck item)
    {
        Truck updated = db.Trucks.Where(x => x.Id == item.Id).FirstOrDefault();
        db.Entry(updated).CurrentValues.SetValues(item);
        return db.SaveChanges();
    }

Answer 1

您收到的错误消息是准确的——您正在设置 _truck.Id 属性，按照惯例，该属性是 Entity Framework 使用的主键/身份字段。如果您使用的是 EF Code First，您可能只想将另一个字段添加到您的数据库和数据模型中，以保存 txtplateNumber.Tag 值。无论哪种方式，您都需要删除将该值设置为 _truck.Id 的代码。