Add the XAttribute to XElement if attribute exists in the element

Question

Need to add

XAttribute newatt = new XAttribute(\"TAG\", value); 

to XElement elem, but the elem could already contai

Answer 1

You don't need to check whether the attribute already exists before using SetAttributeValue. Just:

// Unconditional
elem.SetAttributeValue("TAG", value);

(There's no point even creating the XAttribute yourself.)

From the documentation:

The value is assigned to the attribute with the specified name. If no attribute with the specified name exists, a new attribute is added. If the value is null, the attribute with the specified name, if any, is deleted.