Drawing on Canvas (Web application, C#, ASP.Net)

Hello, We currently have an online application built in C#.Net / ASP Web forms, which needs a drawing element added. The user needs to be able to draw a simple flow chart, using standard shapes, add lines (that don't necessarily connect directly to shapes), select and resize some basic shapes, add text and save on a transparent background back to our application. Lines and shapes need to be selectable, draggable and resizable. 4 colours are essential (black, red, green, blue) for all shapes, lines and text. This is very urgent. Please provide a cost for developing this piece of functionality. This is a product that will have more functionality added in the future so there is also the possibility for future streams of work. Also, can you please provide some examples of similar work when applying. Kind Regards, Ian