关于这篇文章的标题我斟酌了很久，总觉得不管用哪个标题，都很难用不多的文字准确的描述其内容，最后还是觉得用这样一个标题吧。
先谈谈最近我们项目团队中遇到的两个需求：
1、有很多地方都需要在表格或者列表中实现多选，比如有一个人员列表，对应的数据源假设是List<EmployeeInfo>，要想实现多选，第一感觉就是在EmployeeInfo中增加Boolean Selected这样一个属性，这样固然可以解决问题，但在其他地方根本就用不到这个属性，而且如果后面还是其他类似的问题的话，EmployeeInfo这个类就会变得越来越大，越来越臃肿，于是乎就增加了下面的类：
public class SelectableInfo<T>
{
public Boolean Selected { get; set; }
public T Value { get; set; }
}
似乎这样可以解决问题，但在与UI控件绑定的时候出现了问题，将类似"Value.Name"这样的值作为PropertyName时根本不被识别。
2、在项目中某个地方需要有一个日程表，比如纵轴是人员，横轴是日期，但横轴是不固定的，日期范围是可以由用户自由选择的，于是乎设计了类似下面的数据结构：
public class ScheduleItem<TMain, TItem>
{
public ScheduleItem()
{
this.Items = new List<TItem>();
}
public TMain Main { get; set; }
public List<TItem> Items { get; private set; }
}
似乎这样的话就可以直接用一个List<ScheduleItem<EmployeeInfo, EmployeeScheduleItemInfo>>作为UI控件的数据源，动态的将"Main.Name", "Items[0].Name", "Items[1].Name", ..., "Items[n].Name"作为绑定列就能解决问题了，但跟上面的问题一样，这些PropertyName在运行时根本不被识别。
当然，对上面的两个问题，如果直接将DataTable作为数据源，当然这些问题也就都不存在了，但DataTable本身只能算是是一个弱类型对象的List，至于弱类型对象与强类型对象之间的优缺点，就不在此篇文章的讨论范围内了，也无意就此说明或者解释些什么，就事论事，只是想解决类似的问题。
我也在网上找了一下相关的解决方案，似乎只有这一篇文章http://blogs.msdn.com/b/msdnts/archive/2007/01/19/how-to-bind-a-datagridview-column-to-a-second-level-property-of-a-data-source.aspx谈到了类似的问题，并且给出了解决方案，我也仔细拜读了这篇文章，并按他的方法尝试了一番，确实能解决部分问题，但总觉得其实现方式不慎完美，其一，他是通过TypeDescriptionProviderAttribute来实现的，而在.NET FrameWork中，对Attribute的使用是有一些限制的，比如Attribute不支持泛型声明，也不支持变量，灵活性总共不高，其二，总觉得这种方式其实某种程度上可以理解为“篡改”了元数据，很难说会不会对系统其他地方的运行带来问题，比如在反射该类型时等等诸如此类的地方还是有可能会出问题的。
后来在csdn上看到有人也问到类似的问题，有一位高人提到可以用ITypedList实现，但大概一般高人都习惯性的点到为止，并没有给出完整的解决方案。只好仔细的研究了一下ITypedList的相关内容，最终总算是折腾出了一个自己还比较满意的解决方案，代码不是很复杂，也就懒得去一一说明了。
下面是我的解决方案：
using System;
using System.Collections;
using System.Collections.Generic;
using System.ComponentModel;
using System.Linq;
using System.Text.RegularExpressions;
namespace DynamicBinding
{
public class PropertyBindingList<T> : BindingList<T>, ITypedList
{
private List<String> bindProperties;
private Dictionary<String, PropertyDescriptor> propertyDescriptorDictionary;
public PropertyBindingList()
{
this.bindProperties = new List<String>();
this.innerPropertyDescriptorCollection = TypeDescriptor.GetProperties(typeof(T));
this.propertyDescriptorDictionary = new Dictionary<String, PropertyDescriptor>();
}
public void AddBindProperty(String propertyName)
{
if (this.bindProperties.Contains(propertyName))
{
throw new ArgumentException(String.Format(@"The property ""{0}"" is already exists.", propertyName), "propertyName");
}
this.bindProperties.Add(propertyName);
}
public void RemoveBindProperty(String propertyName)
{
this.bindProperties.Remove(propertyName);
}
private PropertyDescriptorCollection innerPropertyDescriptorCollection;
public PropertyDescriptorCollection GetItemProperties(PropertyDescriptor[] listAccessors)
{
var array = new PropertyDescriptor[this.innerPropertyDescriptorCollection.Count + this.bindProperties.Count];
this.innerPropertyDescriptorCollection.CopyTo(array, 0);
for (var i = 0; i < this.bindProperties.Count; i++)
{
array[this.innerPropertyDescriptorCollection.Count + i] = this.GetPropertyDescriptor(this.bindProperties[i]);
}
return new PropertyDescriptorCollection(array);
}
private PropertyDescriptor GetPropertyDescriptor(String propertyPath)
{
if (String.IsNullOrEmpty(propertyPath))
{
throw new ArgumentNullException("propertyPath");
}
var array = propertyPath.Split(‘.‘);
var first = array.First();
var propertyDescriptor = this.GetPropertyDescriptor(this.innerPropertyDescriptorCollection, first);
for (var i = 1; i < array.Length; i++)
{
propertyDescriptor = this.CreatePropertyDescriptor(propertyDescriptor, array[i]);
}
return propertyDescriptor;
}
private PropertyDescriptor GetPropertyDescriptor(PropertyDescriptorCollection propertyDescriptorCollection, String name)
{
var regex = new Regex(@"(?<name>\w+)\[(?<index>\d+)\]");
var match = regex.Match(name);
if (match.Success)
{
var propertyName = match.Groups["name"].Value;
var indexText = match.Groups["index"].Value;
var index = Int32.Parse(indexText);
var arrayPropertyDescriptor = propertyDescriptorCollection[propertyName];
if (arrayPropertyDescriptor == null)
{
throw new ArgumentOutOfRangeException(String.Format(@"Can not find property descriptor ""{0}"" in propertyDescriptorCollection.", propertyName));
}
var itemPropertyDescriptorName = String.Format("{0}[{1}]", arrayPropertyDescriptor.Name, index);
PropertyDescriptor itemPropertyDescriptor;
if (!this.propertyDescriptorDictionary.TryGetValue(itemPropertyDescriptorName, out itemPropertyDescriptor))
{
itemPropertyDescriptor = new InnerItemPropertyDescriptor(
itemPropertyDescriptorName,
arrayPropertyDescriptor,
index);
this.propertyDescriptorDictionary.Add(itemPropertyDescriptorName, itemPropertyDescriptor);
}
return itemPropertyDescriptor;
}
else
{
var result = propertyDescriptorCollection[name];
if (result == null)
{
throw new ArgumentOutOfRangeException(String.Format(@"Can not find property descriptor ""{0}"" in propertyDescriptorCollection.", name));
}
return result;
}
}
private PropertyDescriptor CreatePropertyDescriptor(PropertyDescriptor parentPropertyDescriptor, String name)
{
var regex = new Regex(@"(?<name>\w+)\[(?<index>\d+)\]");
var match = regex.Match(name);
if (match.Success)
{
var propertyName = match.Groups["name"].Value;
var indexText = match.Groups["index"].Value;
var index = Int32.Parse(indexText);
var propertyDescriptorName = parentPropertyDescriptor.Name + "." + propertyName;
PropertyDescriptor arrayPropertyDescriptor;
if (!this.propertyDescriptorDictionary.TryGetValue(propertyDescriptorName, out arrayPropertyDescriptor))
{
var properties = TypeDescriptor.GetProperties(parentPropertyDescriptor.PropertyType);
var valuePropertyDescriptor = properties[propertyName];
if (valuePropertyDescriptor == null)
{
throw new ArgumentOutOfRangeException(String.Format(@"Can not find property descriptor ""{0}"" in type ""{1}"".", propertyName, parentPropertyDescriptor.PropertyType));
}
arrayPropertyDescriptor = new InnerPropertyDescriptor(propertyDescriptorName,
parentPropertyDescriptor,
valuePropertyDescriptor);
this.propertyDescriptorDictionary.Add(propertyDescriptorName, arrayPropertyDescriptor);
}
var itemPropertyDescriptorName = String.Format("{0}[{1}]", arrayPropertyDescriptor.Name, index);
PropertyDescriptor itemPropertyDescriptor;
if (!this.propertyDescriptorDictionary.TryGetValue(itemPropertyDescriptorName, out itemPropertyDescriptor))
{
itemPropertyDescriptor = new InnerItemPropertyDescriptor(
itemPropertyDescriptorName,
arrayPropertyDescriptor,
index);
this.propertyDescriptorDictionary.Add(itemPropertyDescriptorName, itemPropertyDescriptor);
}
return itemPropertyDescriptor;
}
else
{
var propertyDescriptorName = parentPropertyDescriptor.Name + "." + name;
PropertyDescriptor propertyDescriptor;
if (!this.propertyDescriptorDictionary.TryGetValue(propertyDescriptorName, out propertyDescriptor))
{
var properties = TypeDescriptor.GetProperties(parentPropertyDescriptor.PropertyType);
var valuePropertyDescriptor = properties[name];
if (valuePropertyDescriptor == null)
{
throw new ArgumentOutOfRangeException(String.Format(@"Can not find property descriptor ""{0}"" in type ""{1}"".", name, parentPropertyDescriptor.PropertyType));
}
propertyDescriptor = new InnerPropertyDescriptor(
propertyDescriptorName,
parentPropertyDescriptor,
valuePropertyDescriptor);
this.propertyDescriptorDictionary.Add(propertyDescriptorName, propertyDescriptor);
}
return propertyDescriptor;
}
}
public String GetListName(PropertyDescriptor[] listAccessors)
{
return typeof(T).Name;
}
private abstract class BasePropertyDescriptor : PropertyDescriptor
{
public BasePropertyDescriptor(String name)
: base(name, null)
{
}
public override bool IsReadOnly { get { return false; } }
public override void ResetValue(object component) { }
public override bool CanResetValue(object component) { return false; }
public override bool ShouldSerializeValue(object component) { return true; }
}
private class InnerPropertyDescriptor : BasePropertyDescriptor
{
public InnerPropertyDescriptor(String name, PropertyDescriptor parentPropertyDescriptor, PropertyDescriptor valuePropertyDescriptor)
: base(name)
{
this.ParentPropertyDescriptor = parentPropertyDescriptor;
this.ValuePropertyDescriptor = valuePropertyDescriptor;
}
public PropertyDescriptor ParentPropertyDescriptor { get; private set; }
public PropertyDescriptor ValuePropertyDescriptor { get; private set; }
public override Type ComponentType { get { return this.ParentPropertyDescriptor.PropertyType; } }
public override Type PropertyType { get { return this.ValuePropertyDescriptor.PropertyType; } }
public override object GetValue(object component)
{
var parentPropertyValue = this.ParentPropertyDescriptor.GetValue(component);
if (parentPropertyValue != null)
{
return this.ValuePropertyDescriptor.GetValue(parentPropertyValue);
}
return null;
}
public override void SetValue(object component, object value)
{
var parentPropertyValue = this.ParentPropertyDescriptor.GetValue(component);
if (parentPropertyValue != null)
{
this.ValuePropertyDescriptor.SetValue(parentPropertyValue, value);
this.OnValueChanged(component, EventArgs.Empty);
}
}
}
private class InnerItemPropertyDescriptor : BasePropertyDescriptor
{
public InnerItemPropertyDescriptor(String name, PropertyDescriptor parentPropertyDescriptor, Int32 index)
: base(name)
{
this.ParentPropertyDescriptor = parentPropertyDescriptor;
this.Index = index;
}
public PropertyDescriptor ParentPropertyDescriptor { get; private set; }
public Int32 Index { get; private set; }
public override Type ComponentType { get { return this.ParentPropertyDescriptor.PropertyType; } }
public override Type PropertyType { get { return this.ParentPropertyDescriptor.PropertyType.GetElementType(); } }
public override object GetValue(object component)
{
var parentPropertyValue = this.ParentPropertyDescriptor.GetValue(component) as IList;
if (parentPropertyValue != null && parentPropertyValue.Count > this.Index)
{
return parentPropertyValue[this.Index];
}
return null;
}
public override void SetValue(object component, object value)
{
var parentPropertyValue = this.ParentPropertyDescriptor.GetValue(component) as IList;
if (parentPropertyValue != null && parentPropertyValue.Count > this.Index)
{
parentPropertyValue[this.Index] = value;
this.OnValueChanged(component, EventArgs.Empty);
}
}
}
}
}
以下是测试示例：
using System;
using System.Collections.Generic;
using System.Linq;
using System.Windows.Forms;
namespace DynamicBinding
{
static class Program
{
[STAThread]
static void Main()
{
Application.EnableVisualStyles();
Application.SetCompatibleTextRenderingDefault(false);
Application.Run(new TestForm());
}
}
partial class TestForm
{
private System.ComponentModel.IContainer components = null;
protected override void Dispose(bool disposing)
{
if (disposing && (components != null))
{
components.Dispose();
}
base.Dispose(disposing);
}
#region Windows 窗体设计器生成的代码
private void InitializeComponent()
{
this.dataGridView1 = new System.Windows.Forms.DataGridView();
((System.ComponentModel.ISupportInitialize)(this.dataGridView1)).BeginInit();
this.SuspendLayout();
//
// dataGridView1
//
this.dataGridView1.ColumnHeadersHeightSizeMode = System.Windows.Forms.DataGridViewColumnHeadersHeightSizeMode.AutoSize;
this.dataGridView1.Dock = System.Windows.Forms.DockStyle.Fill;
this.dataGridView1.Location = new System.Drawing.Point(0, 0);
this.dataGridView1.Name = "dataGridView1";
this.dataGridView1.RowTemplate.Height = 23;
this.dataGridView1.Size = new System.Drawing.Size(784, 562);
this.dataGridView1.TabIndex = 0;
//
// Form1
//
this.AutoScaleDimensions = new System.Drawing.SizeF(6F, 12F);
this.AutoScaleMode = System.Windows.Forms.AutoScaleMode.Font;
this.ClientSize = new System.Drawing.Size(784, 562);
this.Controls.Add(this.dataGridView1);
this.Name = "TestForm";
this.Text = "TestForm";
((System.ComponentModel.ISupportInitialize)(this.dataGridView1)).EndInit();
this.ResumeLayout(false);
}
#endregion
private System.Windows.Forms.DataGridView dataGridView1;
}
public partial class TestForm : Form
{
public TestForm()
{
InitializeComponent();
}
protected override void OnLoad(EventArgs e)
{
this.dataGridView1.AutoGenerateColumns = true;
var list = new PropertyBindingList<TestA>();
list.AddBindProperty("List[0].BID");
list.AddBindProperty("List[0].List[0].CID");
list.AddBindProperty("List[0].List[0].CName");
list.AddBindProperty("List[0].List[1].CID");
list.AddBindProperty("List[0].List[1].CName");
list.AddBindProperty("List[1].BName");
list.AddBindProperty("List[1].List[0].CID");
list.AddBindProperty("List[1].List[0].CName");
list.AddBindProperty("List[1].List[1].CID");
list.AddBindProperty("List[1].List[1].CName");
list.Add(new TestA
{
AID = 1,
AName = "A001",
List = new TestB[]
{
new TestB
{
BID = 11,
BName = "B11",
List = new TestC[]
{
new TestC
{
CID = 111,
CName = "C111"
},
new TestC
{
CID = 112,
CName = "C112"
}
}
},
new TestB
{
BID = 12,
BName = "B12",
List = new TestC[]
{
new TestC
{
CID = 113,
CName = "C113"
},
new TestC
{
CID = 114,
CName = "C114"
}
}
},
new TestB
{
BID = 13,
BName = "B13"
}
}
});
list.Add(new TestA
{
AID = 1,
AName = "A001"
});
this.dataGridView1.DataSource = list;
base.OnLoad(e);
}
}
public class TestA
{
public Int32 AID
{
get;
set;
}
public String AName
{
get;
set;
}
public TestB[] List
{
get;
set;
}
}
public class TestB
{
public Int32 BID
{
get;
set;
}
public String BName
{
get;
set;
}
public TestC[] List
{
get;
set;
}
}
public class TestC
{
public Int32 CID
{
get;
set;
}
public String CName
{
get;
set;
}
}
}
以下是测试结果：
时间： 2024-11-05 21:30:32