如何在C#中转换为通用参数？

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<TElementType>(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);
        }
    }
}

正如您在GetElementValue的第一个尝试行中看到的那样,我正试图从字符串 – >对象 – > TElementType.不幸的是,这不适用于整数测试用例.运行以下测试时：

[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<int>(xElement,elementName);

    Assert.AreEqual(expectedValue,value,"Expected integer value was not returned from element.");
}

GetElementValue< int>时出现以下异常叫做：

System.InvalidCastException : Cannot cast element value ‘5’ to type ‘Int32’.

我是否必须分别处理每个铸造案例(或至少是数字案例)？