Hey, may I know which dot net framework class can i use if i want to edit some attributes' value in some elements in an xml document?

For example, i want to change the rgb() value inside the following element to rgb(29,23,1):

<line x1="340" y1="155" x2="159" y2="1" style="fill:none;stroke:rgb(0,0,0);stroke-width:5"/>

Please tell me what should i do. Thank you