Dapper.NET Basic Usage


It isn't always possible to neatly package all the parameters up in a single object / call. To help with more complicated scenarios, dapper allows the param parameter to be an IDynamicParameters instance. If you do this, your custom AddParameters method is called at the appropriate time and handed the command to append to. In most cases, however, it is sufficient to use the pre-existing DynamicParameters type:

var p = new DynamicParameters(new { a = 1, b = 2 });
p.Add("c", dbType: DbType.Int32, direction: ParameterDirection.Output);
connection.Execute(@"set @c = @a + @b", p);
int updatedValue = p.Get<int>("@c");

This shows:

  • (optional) population from an existing object
  • (optional) adding additional parameters on the fly
  • passing the parameters to the command
  • retrieving any updated value after the command has finished

Note that due to how RDBMS protocols work, it is usually only reliable to obtain updated parameter values after any data (from a Query or QueryMultiple` operation) has been fully consumed (for example, on SQL Server, updated parameter values are at the end of the TDS stream).