Should you care about the "UseMimeData" property on the .NET ADF Map control?
The ‘UseMimeData’ property tells the ADF whether to request a stream of bytes or a URL. This property is set to TRUE by default. In this case, the ADF is going to store the stream of bytes for the map images into the session storage. If the property is set to false, the image is written to disk in the virtual directory specified and passed back to the browser as a URL. Setting the ‘UseMimeData’ property to TRUE and streaming images from the session is fine when the in-process session storage is used. But other providers like SQL Server is used for storing the session, it is wise to set this property to FALSE and return URLs. This will save the added overhead of serializing everything into the SQL database on each map draw or other draw operations. Setting this property to FALSE will force the MapServer to use its output directory to write out the images and the associated URL will be passed on to the browser. When specifying the path for the virtual directory property on the map control, specify a relative path as an absolute path doesn’t seem to work.