Asp.net mvc 即使代码运行正常，也无法将数据更新到数据库

这是我写的代码。在Quick Watch中查看，一切正常，但数据库没有更新

在updatedata.aspx.cs中

using (var dc = new TrainingEntities())
      {
        var oldData = dc.tr_schools.ToList();
        var newData = oldData.Select(o => new tr_schools()
          {
            banner = o.banner,
            imageOff = o.imageOff,
            imageOn = o.imageOn,
            name = o.name,
            schoolUID = o.schoolUID,
            sequence = o.sequence,
            title = o.title,
            tr_modulesToSchools = o.tr_modulesToSchools,
            type = o.type
          }).ToList();
        newData[0].name = newData[0].name + "XYZ";
        newData[1].name = newData[1].name + "ABC";
        var contents = dc.tr_Content.ToList();

        foreach (var entryold in oldData)
        {
          foreach (var entrynew in newData)
          {
            if (entrynew.schoolUID == entryold.schoolUID && entrynew.name != entryold.name)
            {
              string filter = "-Courses- School " + entryold.name + " Banner Image";
              var schoolContents = contents.Where(p => p.Label.Contains(filter));
              foreach (var schoolContent in schoolContents)
              {
                schoolContent.Label = schoolContent.Label.Replace(entryold.name, entrynew.name);

              }
            }
          }
        }

        dc.SaveChanges();

我在这里做的是通过在数据库中查找旧标签并用新标签替换来更新标签

我的连接字符串：

<connectionStrings>
<add name="TrainingConnectionString" connectionString="Data Source=.\SQLEXPRESS;Initial Catalog=ABCD;User ID=***;Password=*****;" providerName="System.Data.SqlClient" />
<add name="TrainingEntities" connectionString="metadata=res://*/Models.DAL.TrainingEntities.csdl|res://*/Models.DAL.TrainingEntities.ssdl|res://*/Models.DAL.TrainingEntities.msl;provider=System.Data.SqlClient;provider connection string=&quot;data source=.\SQLEXPRESS;initial catalog=ABCD;user id=***;password=*****;MultipleActiveResultSets=True;App=EntityFramework&quot;" providerName="System.Data.EntityClient" />

尝试添加此项

        dc.Entry(oldData).State = EntityState.Modified;
        dc.SaveChanges();

或

        dc.Entry(oldData).CurrentValues.SetValues(newData);
        dc.SaveChanges();