Validate if there is a record in a DB table and store in a variable

I am making a query to validate if there is a record in the database, for this I used the following

I declare variable

decimal serie= 10002;//este valor corresponde a un ejemplo, la variable puede tomar cualquier valor

I make the query

string sql2 = "SELECT codigo from tabla2 WHERE codigo=@serie";

My intention is to capture that value of the code field in the following variable

var camp = db.Database.SqlQuery<decimal>(sql2);

try it that way, that I have to modify so that I can capture that value in that variable