也许你已经尝试过了，但你可以创建一个自定义类：
public class GenericForm<TObject> : Form where TObject : class
{
// Here you can do whatever you want,
// exactly like the example code in the
// first lines of your question
public TObject GenericType { get; set; }
public GenericForm()
{
// To show that this actually works,
// I'll handle the Paint event, because
// it is executed AFTER the window is shown.
Paint += GenericForm_Paint;
}
private void GenericForm_Paint(object sender, EventArgs e)
{
// Let's print the type of TObject to see if it worked:
MessageBox.Show(typeof(TObject).ToString());
}
}
如果你像这样创建它的一个实例：
var form = new GenericForm<string>();
form.Show();
结果是：
更进一步，您可以使用Activator 类从GenericForm 类中创建TObject 类型的实例：
GenericType = (TObject)Activator.CreateInstance(typeof(TObject));
在这个例子中，既然我们知道这是一个字符串，我们也知道它应该抛出一个异常，因为字符串没有无参数的构造函数。所以，让我们改用 char 数组 (char[]) 构造函数：
GenericType = (TObject)Activator.
CreateInstance(typeof(TObject), new char[] { 'T', 'e', 's', 't' });
MessageBox.Show(GenericType as string);
结果：
那我们做作业吧。下面的代码应该可以实现你想要的。
public class Parent
{
string Name { get; set; }
bool HasChildren { get; set; }
int Age { get; set; }
}
public class Child
{
string Name { get; set; }
int Age { get; set; }
}
public class DataController<TObject> where TObject : class
{
protected DbContext _context;
public DataController(DbContext context)
{
_context = context;
}
}
public class FormController<TObject> where TObject : class
{
private DataController<TObject> _dataController;
public FormController(Button btn, DataController<TObject> dataController)
{
_dataController = dataController;
btn.Click += new EventHandler(btnClick);
}
private void btnClick(object sender, EventArgs e)
{
GenericForm<TObject> form = new GenericForm<TObject>();
form.ShowDialog();
}
}
public class GenericForm<TObject> : Form where TObject : class
{
public TObject GenericType { get; set; }
public GenericForm()
{
Paint += GenericForm_Paint;
}
private void GenericForm_Paint(object sender, EventArgs e)
{
MessageBox.Show(typeof(TObject).ToString());
// If you want to instantiate:
GenericType = (TObject)Activator.CreateInstance(typeof(TObject));
}
}
但是，查看您当前的示例，您有两个类，Parent 和 Child。如果我理解正确，那是TObject 类型的唯一可能性。
如果是这种情况，那么如果有人将string 作为类型参数传递（当执行到达Activator.CreateInstance），上面的代码就会爆炸——出现运行时异常（因为string 没有无参数构造函数）：
为了保护您的代码免受这种情况的影响，我们可以在可能的类中继承一个接口。这将导致编译时异常，这是可取的：
代码如下。
// Maybe you should give a better name to this...
public interface IAllowedParamType { }
// Inherit all the possible classes with that
public class Parent : IAllowedParamType
{
string Name { get; set; }
bool HasChildren { get; set; }
int Age { get; set; }
}
public class Child : IAllowedParamType
{
string Name { get; set; }
int Age { get; set; }
}
// Filter the interface on the 'where'
public class DataController<TObject> where TObject : class, IAllowedParamType
{
protected DbContext _context;
public DataController(DbContext context)
{
_context = context;
}
}
public class FormController<TObject> where TObject : class, IAllowedParamType
{
private DataController<TObject> _dataController;
public FormController(Button btn, DataController<TObject> dataController)
{
_dataController = dataController;
btn.Click += new EventHandler(btnClick);
}
private void btnClick(object sender, EventArgs e)
{
GenericForm<TObject> form = new GenericForm<TObject>();
form.ShowDialog();
}
}
public class GenericForm<TObject> : Form where TObject : class, IAllowedParamType
{
public TObject GenericType { get; set; }
public GenericForm()
{
Paint += GenericForm_Paint;
}
private void GenericForm_Paint(object sender, EventArgs e)
{
MessageBox.Show(typeof(TObject).ToString());
// If you want to instantiate:
GenericType = (TObject)Activator.CreateInstance(typeof(TObject));
}
}
更新
正如 RupertMorrish 所说，您仍然可以编译以下代码：
public class MyObj : IAllowedParamType
{
public int Id { get; set; }
public MyObj(int id)
{
Id = id;
}
}
这仍然应该引发异常，因为您刚刚删除了隐式无参数构造函数。当然，如果你知道自己在做什么，这很难发生，但是我们可以通过在 'where' 类型过滤上使用 new() 来禁止这种情况 - 同时也摆脱 Activator.CreateInstance 的东西。
整个代码：
// Maybe you should give a better name to this...
public interface IAllowedParamType { }
// Inherit all the possible classes with that
public class Parent : IAllowedParamType
{
string Name { get; set; }
bool HasChildren { get; set; }
int Age { get; set; }
}
public class Child : IAllowedParamType
{
string Name { get; set; }
int Age { get; set; }
}
// Filter the interface on the 'where'
public class DataController<TObject> where TObject : new(), IAllowedParamType
{
protected DbContext _context;
public DataController(DbContext context)
{
_context = context;
}
}
public class FormController<TObject> where TObject : new(), IAllowedParamType
{
private DataController<TObject> _dataController;
public FormController(Button btn, DataController<TObject> dataController)
{
_dataController = dataController;
btn.Click += new EventHandler(btnClick);
}
private void btnClick(object sender, EventArgs e)
{
GenericForm<TObject> form = new GenericForm<TObject>();
form.ShowDialog();
}
}
public class GenericForm<TObject> : Form where TObject : new(), IAllowedParamType
{
public TObject GenericType { get; set; }
public GenericForm()
{
Paint += GenericForm_Paint;
}
private void GenericForm_Paint(object sender, EventArgs e)
{
MessageBox.Show(typeof(TObject).ToString());
// If you want to instantiate:
GenericType = new TObject();
}
}