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POhow to dynamically create binding proxies?
 

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    <p>I don't know if I asked it right, but I'm kind of lost for hours, so bare with me.</p> <p>My initial problem was: I have a configuration object, which has an <code>enum</code> and I wanted to bind a bunch of <code>RadioButton</code>'s to the same property. As I see myself repeating it sometimes I tried to come up with a general solution for binding multiple items to the same property. The solution I found was to create a proxy which executes an expression. See the code below.</p> <pre><code>public enum GenderEnum { Male, Female } public class DataClass { public GenderEnum Gender { get; set; } } class ExpressionBinder&lt;T&gt; { public Func&lt;T&gt; Getter; public Action&lt;T&gt; Setter; public T Value { get { return Getter.Invoke(); } set { Setter.Invoke(value); } } public ExpressionBinder(Func&lt;T&gt; getter, Action&lt;T&gt; setter) { Getter = getter; Setter = setter; } } </code></pre> <p>I can use it this way:</p> <pre><code>radioMale.Tag = GenderEnum.Male; radioFemale.Tag = GenderEnum.Female; var proxyM = new ExpressionBinder&lt;bool&gt;( () =&gt; DataObj.Gender == (GenderEnum)radioMale.Tag, (val) =&gt; { if (val) DataObj.Gender = (GenderEnum)radioMale.Tag; }); var proxyF = new ExpressionBinder&lt;bool&gt;( () =&gt; DataObj.Gender == (GenderEnum)radioFemale.Tag, (val) =&gt; { if (val) DataObj.Gender = (GenderEnum)radioFemale.Tag; }); radioMale.DataBindings.Add("Checked", proxyM, "Value"); radioFemale.DataBindings.Add("Checked", proxyF, "Value"); </code></pre> <p>It's just an example, I wanted to keep it simple. But this approach actually <strong>WORKS</strong>. By question is:</p> <p>I want to encapsulate the comparison and set expressions inside a derived class. </p> <pre><code>class ComparisonBinder : ExpressionBinder {} </code></pre> <p>Unfortunately, I can only say how I would like to use it.</p> <pre><code>radioMale.DataBindings.Add("Checked", new ComparisonBinder&lt;ConfigClass&gt;((c) c.Gender, GenderEnum.Male), "Value"); radioFemale.DataBindings.Add("Checked", new ComparisonBinder&lt;ConfigClass&gt;((c) c.Gender, GenderEnum.Female), "Value"); </code></pre> <p>So, how would you implement this? Feel free to change my ExpressionBinder class if you need to.</p> <hr> <hr> <p><strong>The Final code</strong></p> <p>(edited again: you can't omit the TValue parameter using object type. During the conversion of the lambda expression the compiler will add a call to <code>Convert()</code>.)</p> <pre><code>class ComparisonBinder&lt;TSource, TValue&gt; : ExpressionBinder&lt;bool&gt; { private TSource instance; private TValue comparisonValue; private PropertyInfo pInfo; public ComparisonBinder(TSource instance, Expression&lt;Func&lt;TSource, TValue&gt;&gt; property, TValue comparisonValue) { pInfo = GetPropertyInfo(property); this.instance = instance; this.comparisonValue = comparisonValue; Getter = GetValue; Setter = SetValue; } private bool GetValue() { return comparisonValue.Equals(pInfo.GetValue(instance, null)); } private void SetValue(bool value) { if (value) { pInfo.SetValue(instance, comparisonValue,null); } } /// &lt;summary&gt; /// Adapted from surfen's answer (http://stackoverflow.com/a/10003320/219838) /// &lt;/summary&gt; private PropertyInfo GetPropertyInfo(Expression&lt;Func&lt;TSource, TValue&gt;&gt; propertyLambda) { Type type = typeof(TSource); MemberExpression member = propertyLambda.Body as MemberExpression; if (member == null) throw new ArgumentException(string.Format( "Expression '{0}' refers to a method, not a property.", propertyLambda)); PropertyInfo propInfo = member.Member as PropertyInfo; if (propInfo == null) throw new ArgumentException(string.Format( "Expression '{0}' refers to a field, not a property.", propertyLambda)); if (type != propInfo.ReflectedType &amp;&amp; !type.IsSubclassOf(propInfo.ReflectedType)) throw new ArgumentException(string.Format( "Expresion '{0}' refers to a property that is not from type {1}.", propertyLambda, type)); return propInfo; } } </code></pre> <p><strong>Usage:</strong></p> <pre><code>radioMale.DataBindings.Add("Checked", new ComparisonBinder&lt;DataClass,GenderEnum&gt;(DataObj, (x) =&gt; x.Gender, GenderEnum.Male), "Value"); radioFemale.DataBindings.Add("Checked", new ComparisonBinder&lt;DataClass,GenderEnum&gt;(DataObj, (x) =&gt; x.Gender, GenderEnum.Female), "Value"); </code></pre>
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