Question

使用以下代码循环遍历数据库行并使用每次迭代编辑数据时

 var entities = db.entities.Where(l => l.id > 28181 && l.id < 28425 && l.Geometry == null).ToList();
        HttpClient client = new HttpClient();
        HttpResponseMessage response = new HttpResponseMessage();
        foreach (model entity in entities)
        {

            string area = entity.address + " " + entity.city + " " + country;
            var address = String.Format("https://maps.googleapis.com/maps/api/geocode/json?key=AIzaSyArOWaWq_xXjAm68DlFFFqoxK7Z_ggYk9E&address=" + gebied);
            response = await client.GetAsync(address);
            var bekijk = response.StatusCode;
            if (response.IsSuccessStatusCode)
            {
                var data = response.Content.ReadAsStringAsync();
                var jObject = Newtonsoft.Json.Linq.JObject.Parse(data.Result);
                string status = jObject["status"].ToObject<string>();
                if (status== "OK")
                {
                    var geometryLocation = jObject["results"][0]["geometry"]["location"];
                    string lat = geometryLocation["lat"].ToObject<string>();
                    string lon = geometryLocation["lng"].ToObject<string>();
                    entity.Geometry = System.Data.Entity.Spatial.DbGeometry.FromText("POINT(" + lat + " " + lon + ")");
                    entity.Latitude = Convert.ToDecimal(lat.Replace('.', ','));
                    entity.Longitude = Convert.ToDecimal(lon.Replace('.', ','));
                    db.Entry(entity).State = EntityState.Modified;
                }

            }

        }
        db.SaveChanges();

在db.SaveChanges();发生错误。即

存储更新，插入或删除语句会影响意外的行数（0）。自实体加载以来，实体可能已被修改或删除。

我已经尝试过在stackoverflow上看到的解决方案，但没有做到这一点。有人有任何线索吗？提前谢谢。

Answer 1

分配值并以其他方法保存它以某种方式修复它。有人可以告诉我为什么吗？

    public async void FirstMethod()
    {

        var entities = db.entities.ToList();

        HttpClient client = new HttpClient();
        HttpResponseMessage response = new HttpResponseMessage();
        foreach (var entity in entities)
        {

            string area= entity.address + " " + entity.city + " " + land;
            var address = String.Format("https://maps.googleapis.com/maps/api/geocode/json?key=AIzaSyArOWaWq_xXjAm68DlFFFqoxK7Z_ggYk9E&address=" + area);
            response = await client.GetAsync(address);

            if (response.IsSuccessStatusCode)
            {
                var data = response.Content.ReadAsStringAsync();
                var jObject = Newtonsoft.Json.Linq.JObject.Parse(data.Result);
                string status = jObject["status"].ToObject<string>();

                if (status == "OK")
                {
                    var geometryLocation = jObject["results"][0]["geometry"]["location"];
                    string lat = geometryLocation["lat"].ToObject<string>();
                    string lon = geometryLocation["lng"].ToObject<string>();
                    SecondMethod(lat+" "+lon ,entity);
                }
            }
        }
    }


    public void SecondMethod(string preometry, model entity)
    {
        entity.Geometry = System.Data.Entity.Spatial.DbGeometry.FromText("POINT(" + preometry + ")");
        string[] latLon = preometry.Split(' ');
        entity.Latitude = Decimal.Parse(latLon[0].Replace(".", ","));
        entity.Longitude = Decimal.Parse(latLon[1].Replace(".", ","));
        db.Entry(entity).State = EntityState.Modified;
        db.SaveChanges();
    }

Answer 2

您是否尝试手动更新实体？

使用程序包管理器控制台：

PM> Add-Migration MyMigration
...
PM> Update-Database

这可能有所帮助：Automatic Code First Migrations

自实体加载后，实体可能已被修改或删除。使用db.Entry（entity）时.State = EntityState.Modified; SaveChanges（）

2 个答案: