How can I export all table all records in a database into json using C#

Question

I am creating a ERP tool for a supermarket. The owner has two supermarkets in two different places. So, to manage the supermarket the local database (mySQL) should be synchronized to the web server. Currently I am using the following C# code to export all records of a table(sales_products) from my database by filtering the records using columns added_on and last_updated. My database contains more than 20 tables and more records.

private void button1_Click(object sender, EventArgs e)
{
        string json = string.Empty;
        List<object> objects = new List<object>();
        MySqlConnection _dbConnection = new MySqlConnection("Server = localhost; Database = app_erp_suneka; Uid = root; Pwd = ;");
        {
           _dbConnection.Open();// .Open();
           using (MySqlCommand command = _dbConnection.CreateCommand())
            {
                command.CommandText = "SELECT * FROM sales_products";
                using (MySqlDataReader reader = command.ExecuteReader())
                {
                    while (reader.Read())
                    {
                        IDictionary<string, object> record = new Dictionary<string, object>();
                        for (int i = 0; i < reader.FieldCount; i++)
                        {
                            record.Add(reader.GetName(i), reader[i]);
                        }
                        objects.Add(record);
                    }
                }
            }
        }
        json = JsonConvert.SerializeObject(objects);
        using (StreamWriter sw = new StreamWriter(File.Create(@"C:\Users\SAKTHY-PC\Desktop\path.json")))// "C:\\path\\file.json")))
        {
            sw.Write(json);
        }
}

My Question is:

How can I export all records to json file from all tables using C# ?

Answer 1

@Bradley Grainger, Nice to hear. But I can not ensure, that all the time my local dB has least records to use JsonSerializer. In the function time(like New Year or Christmas...), there will be more transactions, so the dB will huge and huge.

Answer 2

JSON only has a limited number of data types (string, floating-point number, Boolean, null); you may lose precision by exporting your MySQL data to JSON (because DATETIME, TIMESTAMP, GUID, BLOB, etc., will have to be converted to a string).

But if you still want to export a database to JSON, first you need to find all the tables in the database (by querying the information_schema.tables table), then iterate over each table, selecting all the rows and dumping them to JSON. Because this may be a lot of data, to avoid running out of memory you'll need to stream the results to your output file (instead of creating a large number of objects in memory then converting them to JSON). This requires using a low-level JSON writing API, so you need to ensure that WriteStartObject and WriteEndObject calls are paired correctly to create valid JSON.

The following program snippet demonstrates this technique:

using (var connection = new MySqlConnection("Server = localhost; Database = app_erp_suneka; Uid = root; Pwd = ;"))
{
    connection.Open();

    // get the names of all tables in the chosen database
    var tableNames = new List<string>();
    using (var command = new MySqlCommand(@"SELECT table_name FROM information_schema.tables where table_schema = @database", connection))
    {
        command.Parameters.AddWithValue("@database", "app_erp_suneka");
        using (var reader = command.ExecuteReader())
        {
            while (reader.Read())
                tableNames.Add(reader.GetString(0));
        }
    }

    // open a JSON file for output; use the streaming JsonTextWriter interface to avoid high memory usage
    using (var streamWriter = new StreamWriter(@"C:\Temp\app_erp_suneka.json"))
    using (var jsonWriter = new JsonTextWriter(streamWriter) { Formatting = Newtonsoft.Json.Formatting.Indented, Indentation = 2, IndentChar = ' ' })
    {
        // one array to hold all tables
        jsonWriter.WriteStartArray();

        foreach (var tableName in tableNames)
        {
            // an object for each table
            jsonWriter.WriteStartObject();
            jsonWriter.WritePropertyName("tableName");
            jsonWriter.WriteValue(tableName);
            jsonWriter.WritePropertyName("rows");

            // an array for all the rows in the table
            jsonWriter.WriteStartArray();

            // select all the data from each table
            using (var command = new MySqlCommand($@"SELECT * FROM `{tableName}`", connection))
            using (var reader = command.ExecuteReader())
            {
                while (reader.Read())
                {
                    // write each row as a JSON object
                    jsonWriter.WriteStartObject();
                    for (int i = 0; i < reader.FieldCount; i++)
                    {
                        jsonWriter.WritePropertyName(reader.GetName(i));
                        jsonWriter.WriteValue(reader.GetValue(i));
                    }
                    jsonWriter.WriteEndObject();
                }
            }

            jsonWriter.WriteEndArray();
            jsonWriter.WriteEndObject();
        }

        jsonWriter.WriteEndArray();
    }
}