vb.net - gdi+ buffer to file -

i have written little program produces nice real time full screen patterns , effects.

as after thought decided add screen grab feature program hitting print screen cause still image of current frame saved disk.

the program uses gdi+ , writes graphics directly form via manually controlled double buffer. this:

dim mcontext bufferedgraphicscontext  dim mbuff bufferedgraphics 

.

mbuff = mcontext.allocate(me.creategraphics, rec) 

.

mbuff.graphics.fillrectangle... , other drawing operations. 

.

mbuff.render 

is there simple way information form or buffer state can write jpg or bmp file, i'm missing?

thanks