强类型 Windows 窗体数据绑定

Question

我正在研究使用扩展方法的强类型 Windows 窗体数据绑定。我从Xavier 得到了如下帮助：

using System;
using System.Linq.Expressions;
using System.Windows.Forms;

namespace WindowsFormsApplication1
{
    public static Binding Add<T>
        (this ControlBindingsCollection dataBindings,
            object dataSource,
            Expression<Func<Control, object>> controlExpression,
            Expression<Func<T, object>> objectExpression)
    {
        return Add(dataBindings, dataSource, controlExpression, objectExpression, false);
    }

    public static Binding Add<T>
        (this ControlBindingsCollection dataBindings,
            object dataSource,
            Expression<Func<Control, object>> controlExpression,
            Expression<Func<T, object>> objectExpression,
            bool formattingEnabled)
    {
        string controlPropertyName = ProcessExpression(controlExpression.Body);
        string bindingTargetName = ProcessExpression(objectExpression.Body);

        return dataBindings
            .Add(controlPropertyName, dataSource, bindingTargetName, formattingEnabled);
    }

    public static Binding Add<T, K>
        (this ControlBindingsCollection dataBindings,
            object dataSource,
            Expression<Func<K, object>> controlExpression,
            Expression<Func<T, object>> objectExpression)
    {
        return Add(dataBindings, dataSource, controlExpression, objectExpression, false);
    }

    public static Binding Add<T, K>
        (this ControlBindingsCollection dataBindings,
            object dataSource,
            Expression<Func<K, object>> controlExpression,
            Expression<Func<T, object>> objectExpression,
            bool formattingEnabled
        )
    {
        string controlPropertyName = ProcessExpression(controlExpression.Body);
        string bindingTargetName = ProcessExpression(objectExpression.Body);

        return dataBindings.Add(controlPropertyName, dataSource, bindingTargetName, formattingEnabled);
    }

    private static string ProcessExpression(Expression expression)
    {
        string propertyName;
        if (expression is MemberExpression)
        {
            propertyName = ((MemberExpression) (expression)).Member.Name;
        }
        else if (expression is UnaryExpression)
        {
            propertyName = ((MemberExpression) ((UnaryExpression) (expression)).Operand).Member.Name;
        }
        else
        {
            throw new InvalidOperationException(
                "Unknown expression type error in DataBindingsExtensionMethods.Add<T, K>");
        }
        return propertyName;
    }
}

现在我可以像这样设置 DataBinding：

txtBoundInt.DataBindings.Add<Contact>
    (bindingSource, tb => tb.Text, contact => contact.Id);

或者这个：

cboBoundSelectedItem.DataBindings.Add
            <Contact, ComboBox>
            (bindingSource, cbo => cbo.SelectedItem, con => con.ContactType)

不过，似乎有很多表达式的转换。有没有更好的办法？

---

编辑：我确实找到了一个更好的方法，但是我把这个问题改成那个答案时遇到了麻烦——@Carl_G 的reproduced below。

Answer 1

将返回类型设置为对象呢？

public static Binding Add<T>
    (this ControlBindingsCollection dataBindings, object dataSource,
    Expression<Func<Control, object>> controlLambda,
    Expression<Func<T, object>> objectLambda) {
    string controlPropertyName =
          ((MemberExpression)(controlLambda.Body)).Member.Name;
    string bindingTargetName =
          ((MemberExpression)(objectLambda.Body)).Member.Name;

    return dataBindings.Add
         (controlPropertyName, dataSource, bindingTargetName);
}

Answer 2

由于问题已被编辑为仅包含答案，因此我将在此处包含该答案。作者可能应该单独离开the original question 并发布他自己问题的答案。但这似乎是一个非常好的解决方案。

---

编辑：我更喜欢我最终找到的这个解决方案in Google's cache（它已从author's site 中删除），因为它只需要一个类型规范。不知道原作者为什么删了。

// Desired call syntax:
nameTextBox.Bind(t => t.Text, aBindingSource, (Customer c) => c.FirstName);

// Binds the Text property on nameTextBox to the FirstName property
// of the current Customer in aBindingSource, no string literals required.

// Implementation.

public static class ControlExtensions
{
    public static Binding Bind<TControl, TDataSourceItem>
        (this TControl control, 
         Expression<Func<TControl, object>> controlProperty, 
         object dataSource, 
         Expression<Func<TDataSourceItem, object>> dataSourceProperty)
         where TControl: Control
    {
        return control.DataBindings.Add
             (PropertyName.For(controlProperty), 
              dataSource, 
              PropertyName.For(dataSourceProperty));
    }
}

public static class PropertyName
{
    public static string For<T>(Expression<Func<T, object>> property)
    {
        var member = property.Body as MemberExpression;
        if (null == member)
        {
            var unary = property.Body as UnaryExpression;
            if (null != unary) member = unary.Operand as MemberExpression;
        }
        return null != member ? member.Member.Name : string.Empty;
    }
}

Answer 3

几个月来，我一直在使用 Stuart 发布的代码。我确实添加了更多的重载来匹配您可能想要使用的其他数据绑定场景（我只是在这里发布它是为了让其他人更容易让这个非常有用的东西工作）

    public static class ControlExtensions {

    /// <summary>Databinding with strongly typed object names</summary>
    /// <param name="control">The Control you are binding to</param>
    /// <param name="controlProperty">The property on the control you are binding to</param>
    /// <param name="dataSource">The object you are binding to</param>
    /// <param name="dataSourceProperty">The property on the object you are binding to</param>
    public static Binding Bind<TControl, TDataSourceItem>(this TControl control, Expression<Func<TControl, object>> controlProperty, object dataSource, Expression<Func<TDataSourceItem, object>> dataSourceProperty)
    where TControl :Control {
        return control.DataBindings.Add(PropertyName.For(controlProperty), dataSource, PropertyName.For(dataSourceProperty));
    }
    public static Binding Bind<TControl, TDataSourceItem>(this TControl control, Expression<Func<TControl, object>> controlProperty, object dataSource, Expression<Func<TDataSourceItem, object>> dataSourceProperty, bool formattingEnabled = false)
    where TControl :Control {
        return control.DataBindings.Add(PropertyName.For(controlProperty), dataSource, PropertyName.For(dataSourceProperty), formattingEnabled);
    }
    public static Binding Bind<TControl, TDataSourceItem>(this TControl control, Expression<Func<TControl, object>> controlProperty, object dataSource, Expression<Func<TDataSourceItem, object>> dataSourceProperty, bool formattingEnabled, DataSourceUpdateMode updateMode)
    where TControl :Control {
        return control.DataBindings.Add(PropertyName.For(controlProperty), dataSource, PropertyName.For(dataSourceProperty), formattingEnabled, updateMode);
    }
    public static Binding Bind<TControl, TDataSourceItem>(this TControl control, Expression<Func<TControl, object>> controlProperty, object dataSource, Expression<Func<TDataSourceItem, object>> dataSourceProperty, bool formattingEnabled, DataSourceUpdateMode updateMode, object nullValue)
    where TControl :Control {
        return control.DataBindings.Add(PropertyName.For(controlProperty), dataSource, PropertyName.For(dataSourceProperty), formattingEnabled, updateMode, nullValue);
    }
    public static Binding Bind<TControl, TDataSourceItem>(this TControl control, Expression<Func<TControl, object>> controlProperty, object dataSource, Expression<Func<TDataSourceItem, object>> dataSourceProperty, bool formattingEnabled, DataSourceUpdateMode updateMode, object nullValue, string formatString)
    where TControl :Control {
        return control.DataBindings.Add(PropertyName.For(controlProperty), dataSource, PropertyName.For(dataSourceProperty), formattingEnabled, updateMode, nullValue, formatString);
    }
    public static Binding Bind<TControl, TDataSourceItem>(this TControl control, Expression<Func<TControl, object>> controlProperty, object dataSource, Expression<Func<TDataSourceItem, object>> dataSourceProperty, bool formattingEnabled, DataSourceUpdateMode updateMode, object nullValue, string formatString, IFormatProvider formatInfo)
    where TControl :Control {
        return control.DataBindings.Add(PropertyName.For(controlProperty), dataSource, PropertyName.For(dataSourceProperty), formattingEnabled, updateMode, nullValue, formatString, formatInfo);
    }

    public static class PropertyName {
        public static string For<T>(Expression<Func<T, object>> property) {
            var member = property.Body as MemberExpression;
            if(null == member) {
                var unary = property.Body as UnaryExpression;
                if(null != unary) member = unary.Operand as MemberExpression;
            }
            return null != member ? member.Member.Name : string.Empty;
        }
    }

}