Dapper and the NVARCHAR(4000) arguments

Performing a profiler in the queries sended to the database you can see that in some cases Dapper is sending the string arguments as NVARCHAR (4000).

Introduction

This happen because Dapper cannot infer what is the exactly type and length of the table column on database.

The downside of the NVARCHAR (4000) in arguments is that the database can choose a bad execution plan for the query.

Solution

To avoid this you can pass the type of the argument to Dapper:

To make this solution easier to use I made two extension methods ToVarChar and ToNVarChar:

Extension methods