Frist Step:-> In Microsoft visual studio file->new->project
Second Step:-> choose project type as c# and template will be class libraries
Third Step:-> the project name was classdll
Fourth Step:-> check the classdll location in your hard disk, there is one folder name was bin->debug-> here only your class file will convert into dll
Fifth Step:-> your file name was class1.cs
Sixth Step:-> first add your libraries whatever you want
Seventh Step:-> it show the error (missing assembly reference) you have to add the some libraries move to
Project->addreference->.net(tab) add your dll files…
Eight Step:->
Above like this
Nineth Step:-> you can placed your .cs coding in the class1 method
public class Class1
{
public long Add(long val1)
{
return val1;
}
}