How to check null values in dataset

if(ds.Tables[0].Rows[0].IsNull(columnName)==true)

{

Response.write("Contains null value")

}

Difference between VB dll and assemblies in .NET

Assemblies can contain DLL and EXE both. Different versions 

of one DLL can be handeled by assemblies. They overcome the 

DLL Hell problem. Assemblies Contain Manifest and MetaData 

files. These are the seprate files that describes the 

Assembly and its attributes. 

VB DLL is inprocess.DLL run with an exe                   

where as DLL are not self executable. 

we can reuse DLLs .DLL are not platform independent

If we have more then one Versions of a DLL we can face DLL Hell Problem.