Microsoft.Office.Interop.Owc11.ChartSpace objCSpace = new Microsoft.Office.Interop.Owc11ChartSpaceClass();

string str ="<OBJECT classid=\"clsid:0002E55D- 0000 - 0000 -C000- 000000000046 \" VIEWASTEXT>" +
"<PARAM NAME=\"XMLData\" VALUE='"+
objCSpace.XMLData +
"'</OBJECT>";

PlaceHolder1.Controls.Add(new LiteralControl(str));

Response.ContentType = "image/gif";
Response.BinaryWrite((byte[])objCSpace.GetPicture("gif",  500 ,  400 ));
Response.End();