I've seen an example here: msdn but it's a little confusing.
So if I have a list definition with a field called "CustomField" and I want to update the "ShowField" attribute of this field to be true then I would do this:
XmlNode listNode = listService.GetList("MyList");
string version = listNode.Attributes["Version"].Value;
string guid = listNode.Attributes["Name"].Value;
XmlDocument xmlDoc = new XmlDocument();
XmlElement updateFields = xmlDoc.CreateElement("Fields");
string fieldXml = @"<Method ID="1"><Field Name="CustomField" ShowField="true" /></Method>";
updateFields.InnerXml = fieldXml;
XmlNode result = listService.UpdateList(guid, null, null, updateFields, null, version);
I'm confused because it would seem that you would need to provide a field element to indicate what field to update and then a value element to specify the new value.
Could someone clarify this please?