当我运行bundle exec rake db:migrate --trace时出现以下错误.
C:\Sites\rails_projects\sample_app>bundle exec rake db:migrate --trace
** Invoke db:migrate (first_time)
** Invoke environment (first_time)
** Execute environment
rake aborted!
undefined method `migration_error=' for ActiveRecord::Base:Class
C:/RailsInstaller/Ruby1.9.3/lib/ruby/gems/1.9.1/gems/activerecord-3.2.14/lib/act
ive_record/dynamic_matchers.rb:55:in `method_missing'
C:/RailsInstaller/Ruby1.9.3/lib/ruby/gems/1.9.1/gems/activerecord-3.2.14/lib/act
ive_record/railtie.rb:72:in `block (3 levels) in <class:Railtie>'
C:/RailsInstaller/Ruby1.9.3/lib/ruby/gems/1.9.1/gems/activerecord-3.2.14/lib/act
ive_record/railtie.rb:71:in `each'
C:/RailsInstaller/Ruby1.9.3/lib/ruby/gems/1.9.1/gems/activerecord-3.2.14/lib/act
ive_record/railtie.rb:71:in `block (2 levels) in <class:Railtie>'
C:/RailsInstaller/Ruby1.9.3/lib/ruby/gems/1.9.1/gems/activesupport-3.2.14/lib/ac
tive_support/lazy_load_hooks.rb:36:in `instance_eval'
C:/RailsInstaller/Ruby1.9.3/lib/ruby/gems/1.9.1/gems/activesupport-3.2.14/lib/ac
tive_support/lazy_load_hooks.rb:36:in `execute_hook'
C:/RailsInstaller/Ruby1.9.3/lib/ruby/gems/1.9.1/gems/activesupport-3.2.14/lib/ac
tive_support/lazy_load_hooks.rb:26:in `block in on_load'
C:/RailsInstaller/Ruby1.9.3/lib/ruby/gems/1.9.1/gems/activesupport-3.2.14/lib/ac
tive_support/lazy_load_hooks.rb:25:in `each'
C:/RailsInstaller/Ruby1.9.3/lib/ruby/gems/1.9.1/gems/activesupport-3.2.14/lib/ac
tive_support/lazy_load_hooks.rb:25:in `on_load'
C:/RailsInstaller/Ruby1.9.3/lib/ruby/gems/1.9.1/gems/activerecord-3.2.14/lib/act
ive_record/railtie.rb:67:in `block in <class:Railtie>'
C:/RailsInstaller/Ruby1.9.3/lib/ruby/gems/1.9.1/gems/railties-3.2.14/lib/rails/i
nitializable.rb:30:in `instance_exec'
C:/RailsInstaller/Ruby1.9.3/lib/ruby/gems/1.9.1/gems/railties-3.2.14/lib/rails/i
nitializable.rb:30:in `run'
C:/RailsInstaller/Ruby1.9.3/lib/ruby/gems/1.9.1/gems/railties-3.2.14/lib/rails/i
nitializable.rb:55:in `block in …我正在使用 Visual Studio 2010 和 C# 创建一个带有组合框的 Windows 窗体，该窗体应包含员工姓名首字母。在过去的几天里，我一直在搜索我能找到的所有解决方案，但仍然无法填充我的组合框。
这是我目前所拥有的：
public static void FillComboBox(string Query, System.Windows.Forms.ComboBox LoggedByBox)
{
using (var CONN = new OleDbConnection("Provider=Microsoft.Jet.OLEDB.4.0;Data Source=C:\\Users\\Documents\\Service Request Application\\bin\\Debug\\servicereq1.mdb"))
{
CONN.Open();
DataTable dt = new DataTable();
try
{
OleDbCommand cmd = new OleDbCommand(Query, CONN);
OleDbDataReader myReader = cmd.ExecuteReader();
dt.Load(myReader);
}
catch (OleDbException e)
{
Console.WriteLine(e.ToString());
Console.ReadLine();
return;
}
LoggedByBox.DataSource = dt;
LoggedByBox.ValueMember = "ID";
LoggedByBox.DisplayMember = "Initials";
}
}
然后我在表单加载时调用它
private void Form1_Load(object sender, EventArgs e)
{
FillComboBox("select ID, Initials from [Fixers …