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POHow to Cast to Generic Parameter in C#?
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  1. POHow to Cast to Generic Parameter in C#?
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    copied!<p>I'm trying to write a generic method for fetching an <code>XElement</code> value in a strongly-typed fashion. Here's what I have:</p> <pre><code>public static class XElementExtensions { public static XElement GetElement(this XElement xElement, string elementName) { // Calls xElement.Element(elementName) and returns that xElement (with some validation). } public static TElementType GetElementValue&lt;TElementType&gt;(this XElement xElement, string elementName) { XElement element = GetElement(xElement, elementName); try { return (TElementType)((object) element.Value); // First attempt. } catch (InvalidCastException originalException) { string exceptionMessage = string.Format("Cannot cast element value '{0}' to type '{1}'.", element.Value, typeof(TElementType).Name); throw new InvalidCastException(exceptionMessage, originalException); } } } </code></pre> <p>As you can see on the <code>First attempt</code> line of <code>GetElementValue</code>, I'm trying to go from string -> object -> TElementType. Unfortunately, this does not work for an integer test case. When running the following test:</p> <pre><code>[Test] public void GetElementValueShouldReturnValueOfIntegerElementAsInteger() { const int expectedValue = 5; const string elementName = "intProp"; var xElement = new XElement("name"); var integerElement = new XElement(elementName) { Value = expectedValue.ToString() }; xElement.Add(integerElement); int value = XElementExtensions.GetElementValue&lt;int&gt;(xElement, elementName); Assert.AreEqual(expectedValue, value, "Expected integer value was not returned from element."); } </code></pre> <p>I get the following exception when <code>GetElementValue&lt;int&gt;</code> is called:</p> <blockquote> <p>System.InvalidCastException : Cannot cast element value '5' to type 'Int32'.</p> </blockquote> <p>Am I going to have to handle each casting case (or at least the numeric ones) separately?</p>
 

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