how to assign string to path of system.drawing.image

Question

i have this code,

myitem.Image = pro.Properties.Resources.wheth_1;

Now,

i want to use 

myitem.Image = "pro.Properties.Resources.wheth" + "_1";

its occur error -> Cannot implicitly convert type 'string' to 'System.Drawing.Image'

path.combine  Or new Uri Not Working.