1

我经常用

using (var context = new SomeDataContext(SomeDataContext.ConnectionString))
{
   ...
}

在哪里

abstract class DataContextBase: DataContext { ... }

partial class SomeDataContext: DataContextBase
{
    public const string DatabaseFile = "blablabla.mdf";
    public static readonly string ConnectionString = string.Format(@"Data Source=(LocalDB)\MSSQLLocalDB;AttachDbFilename={0};Integrated Security=True", DatabaseFile);
}

问题：是否可以隐藏SomeDataContext实例的创建并ConnectionString深入DataContextBase？

我只想在继承的类中定义文件名

partial class SomeDataContext: DataContextBase
{
    public const string DatabaseFile = "blablabla.mdf";
}

并且能够创建这样的实例

var context = SomeDataContext.PropertyInBaseClassWhichCreatesInstanceOfInheritedClass;

PS：我首先添加了我如何尝试克服这个问题（没有成功），但后来我删除了它（我在一个多小时内发布了这篇文章！），因为它让问题变得太吵了。起初看起来很容易，直到你（或者只有我？）尝试解决它。我标记它dbml是因为特定于DataContext事物：你不能使用单例，等等。

4

1 回答 1

1

不幸的是，没有某种virtual static，如果你调用SomeDataContext.StaticPropertyInBaseClass，它编译为与DataContextBase.StaticPropertyInBaseClass. 我认为你能做的最好的事情是这样的：

// upside: simple SomeDataContext.Instance for external users
// downside: more code in SomeDataContext
partial class SomeDataContext : DataContextBase
{
    private const string DatabaseFile = "blablabla.mdf";
    public static SomeDataContext Instance
    {
        get
        {
            return new SomeDataContext(GetConnectionString(DatabaseFile));
        }
    }
}
abstract class DataContextBase
{
    protected static string GetConnectionString(string databaseFile)
    {
        return string.Format(@"Data Source=(LocalDB)\MSSQLLocalDB;AttachDbFilename={0};Integrated Security=True", databaseFile);
    }
}
// e.g. using (var context = SomeDataContext.Instance)

或者

// upside: just one line in child class
// downside: a little harder for external callers, with a little less type safety
// downside: as written, requires child class to have parameterless constructor
partial class SomeDataContext : DataContextBase
{
    protected override string DatabaseFileInternal { get { return "blablabla.mdf"; } }
}
abstract class DataContextBase
{
    protected abstract string DatabaseFileInternal { get; }
    private string ConnectionString
    {
        get
        {
            return string.Format(@"Data Source=(LocalDB)\MSSQLLocalDB;AttachDbFilename={0};Integrated Security=True", DatabaseFileInternal);
        }
    }
    public static T GetInstance<T>() where T : DataContextBase, new()
    {
        using (var tInst = new T())
            return (T)Activator.CreateInstance(typeof(T), tInst.ConnectionString);
    }
}
// e.g. using (var context = DataContextBase.GetInstance<SomeDataContext>())
于 2014-12-04T17:54:22.470 回答