I have two blocks; in each block, I am retrieving the data from a table using command and reader and transforming the data, and then updating the same. What I am looking to extract the common function by passing the table name, type, and transform function to that function from these two blocks
Below is the code for the same,
// Block #1
using var queryProjectSteamSystemsCommand = dbContext.Database.GetDbConnection().CreateCommand();
queryProjectSteamSystemsCommand.CommandText = @"SELECT ""Id""::varchar, ""InitialObject""::varchar from ""DesignHubProjectSteamSystems""";
using var steamSystemProjectsReader = queryProjectSteamSystemsCommand.ExecuteReader();
if (steamSystemProjectsReader.HasRows)
{
while (steamSystemProjectsReader.Read())
{
var id = steamSystemProjectsReader.IsDBNull(0) ? Guid.Empty : Guid.Parse(steamSystemProjectsReader.GetString(0));
var steamSystemJson = steamSystemProjectsReader.IsDBNull(1) ? "null" : steamSystemProjectsReader.GetString(1);
var projSteamSystemInitialObj = JsonConvert.DeserializeObject<OldSteamSystem>(steamSystemJson);
string json = JsonConvert.SerializeObject(TransformProjectSteamSystem(projSteamSystemInitialObj)).Replace("'", "''", StringComparison.Ordinal);
migrationBuilder.Sql($"UPDATE \"DesignHubProjectSteamSystems\" SET \"InitialObject\" = '{json}'::jsonb WHERE \"Id\" = '{id}'");
}
}
steamSystemProjectsReader.Close();
// Block #2
using var queryProjectFuelSystemsCommand = dbContext.Database.GetDbConnection().CreateCommand();
queryProjectFuelSystemsCommand.CommandText = @"SELECT ""Id""::varchar, ""InitialObject""::varchar from ""DesignHubProjectFuelSystems""";
using var fuelSystemProjectsReader = queryProjectFuelSystemsCommand.ExecuteReader();
if (fuelSystemProjectsReader.HasRows)
{
while (fuelSystemProjectsReader.Read())
{
var id = fuelSystemProjectsReader.IsDBNull(0) ? Guid.Empty : Guid.Parse(fuelSystemProjectsReader.GetString(0));
var fuelSystemJson = fuelSystemProjectsReader.IsDBNull(1) ? "null" : fuelSystemProjectsReader.GetString(1);
var projFuelSystemInitialObj = JsonConvert.DeserializeObject<OldFuelSystem>(fuelSystemJson);
string json = JsonConvert.SerializeObject(TransformProjectFuelSystem(projFuelSystemInitialObj)).Replace("'", "''", StringComparison.Ordinal);
migrationBuilder.Sql($"UPDATE \"DesignHubProjectFuelSystems\" SET \"InitialObject\" = '{json}'::jsonb WHERE \"Id\" = '{id}'");
}
}
fuelSystemProjectsReader.Close();
I cannot combine OldSteamSystem
and OldFuelSystem
two classes, which are different. I can't make any familiar interface and abstract class out of these two.
So, could anyone please let me know how to make a common function out of it?
Many thanks in advance!!!
CodePudding user response:
Use generics, and ask for the table name and a method to transform the object.
void DoTheThing<TSystem>(string tableName, Func<TSystem, TSystem> transform)
{
using var command = dbContext.Database.GetDbConnection().CreateCommand();
command.CommandText = @$"SELECT ""Id""::varchar, ""InitialObject""::varchar from ""{tableName}""";
// I know I complain about SQL injection, you get to fix this one...
using var reader = command.ExecuteReader();
if (reader.HasRows)
{
while (reader.Read())
{
var id = reader.IsDBNull(0) ? Guid.Empty : Guid.Parse(reader.GetString(0));
var initialJson = reader.IsDBNull(1) ? "null" : reader.GetString(1);
var initialObj = JsonConvert.DeserializeObject<TSystem>(initialJson);
// this uses the "transform" parameter, IE a method your caller provides
string transformedJson = JsonConvert.SerializeObject(transform(initialObj)).Replace("'", "''", StringComparison.Ordinal);
migrationBuilder.Sql($"UPDATE \"{tableName}\" SET \"InitialObject\" = '{transformedJson}'::jsonb WHERE \"Id\" = '{id}'");
// again, SQL injection
}
}
reader.Close();
}
If the transform
method takes one type and returns a different type, then change the method signature to
void DoTheThing<TSystem, TTransformed>(string tableName, Func<TSystem, TTransformed> transform)