Dapper .NET: Customize Mapping

Question

Model

public class ErrorReport{
    public int? Id {get;set;}
    public ExceptionReport Exception {get;set;}
    public ExceptionReport InnerException {get;set;}
}

public class ExceptionReport{
    public string Type {get; set;}
    public string Message {get; set;}
}

Database

This is the table i want to query from

ErrorReports

• Id: int
• ExceptionType: varchar
• ExceptionMessage: varchar
• InnerExceptionType: varchar
• InnerExceptionMessage: varchar

The problem

So, what i want to do is querying the database and map the results into my model properties. But this doesn't work:

using (var con = ConnectionFactory.CreateConnection(_connectionString))
{
     IEnumerable<ErrorReport> reports = con.Query<ErrorReport>("Select * from ErrorReports");
}

I understand that i have to explicitly say which columns map to which property, so, how can i do that?

Answer 1

You can return your query as dynamic and then map each property to your corresponding complex object.

using (var con = ConnectionFactory.CreateConnection(_connectionString))
{
    List<ErrorReport> reports = 
        con.Query<dynamic>("Select * from ErrorReports")
            .Select(x => new ErrorReport 
            { 
                Id = x.Id, 
                Exception = new ExceptionReport
                {
                    Type = x.ExceptionType,
                    Messsage = x.ExceptionMessage
                },
                InnerException = new ExceptionReport
                {
                    Type = x.InnerExceptionType,
                    Messsage = x.InnerExceptionMessage
                }
            }).ToList();
}