There are several types of templates that you can use with JetBrains Rider:
Live/Surround templates can be used for generating code in existing files and (if there is the
$SELECTION$parameter in the template body) for surrounding code fragments with template code, such as
Each live template is identified by a Shortcut — a short string of characters, e.g. foreach — that you can type right in the editor to invoke the template.
.nullafter an expression and JetBrains Rider will create an
ifstatement that checks the expression to be null. See Postfix Templates for details.
Source templates, which are only available for C#, can be created right in the code of your project as extension methods. As soon as you define a source template, you can pick it up in the completion list of corresponding types, similarly to postfix templates. For more information, see Source Templates
File templates are used to create one or more new files with predefined code, such as a type declaration, unit test, etc. File templates have no shortcuts, they are identified by their descriptions. See Creating Files from Templates for details.
For custom cases, JetBrains Rider provides tools for creating, editing user-defined code templates that can cover any particular aspect of your development practices.