There are some options for this kind of requirement.
1. If both sites are related and no need of any kind of privacy, then you can have connection string of both the database in the both web application. With the use of connection string you can retrieve/submit data to both sites.
2. If both are different and you must have to separate configuration then you can create a web service
Many examples[
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3. You can also create a WCF call.
More Details[
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