替换Xml节点/元素的innertext

First of all this is C#. I am creating a internet dashboard for a small group of colleages in the NHS. Below is an example xml file in which I need to change the innertext of. I need to replace a specific element for example "Workshop1." Because we have a few workshops I cannot afford to use a general writer because it will replace all the information on the XML document with this one bit of code below. First of all this is C#. I am creating a intern