How to get column names from a table in sqlite via PRAGMA (.net / c#)?

Question

I have been struggling to get the right c# code for getting the values after a PRAGMA table_info query.

_{Since my edit with extra code was rejected in this post, I made this question for other people that would otherwise waste hours for a fast solution.}

Answer 1

Assuming you want a DataTable with the list of field of your table:

 using (var con = new SQLiteConnection(preparedConnectionString))
    {
       using (var cmd = new SQLiteCommand("PRAGMA table_info(" + tableName + ");"))
        {
            var table = new DataTable();

            cmd.Connection = con;
            cmd.Connection.Open();

             SQLiteDataAdapter adp = null;
                try
                {
                    adp = new SQLiteDataAdapter(cmd);
                    adp.Fill(table);
                    con.Close();
                    return table;
                }
              catch (Exception ex)
              { }
         }
     }

Return result is:

• cid: id of the column
• name: the name of the column
• type: the type of the column
• notnull: 0 or 1 if the column can contains null values
• dflt_value: the default value
• pk: 0 or 1 if the column partecipate to the primary key

If you want only the column names into a List you can use (you have to include System.Data.DataSetExtension):

 return table.AsEnumerable().Select(r=>r["name"].ToString()).ToList();

EDIT: Or you can avoid the DataSetExtension reference using this code:

using (var con = new SQLiteConnection(preparedConnectionString))
      {
          using (var cmd = new SQLiteCommand("PRAGMA table_info(" + tableName + ");"))
          {
              var table = new DataTable();
              cmd.Connection = con;
              cmd.Connection.Open();

              SQLiteDataAdapter adp = null;
              try
              {
                  adp = new SQLiteDataAdapter(cmd);
                  adp.Fill(table);
                  con.Close();
                  var res = new List<string>();
                  for(int i = 0;i<table.Rows.Count;i++)
                      res.Add(table.Rows[i]["name"].ToString());
                  return res;
              }
              catch (Exception ex){ }
          }
      }
      return new List<string>();

There are a lot of PRAGMA statements that you can use in SQLite, have a look at the link.

About the using statement: it's very simple, it is used to be sure that disposable objects will be disposed whatever can happen in your code: see this link or this reference

Answer 2

Code:

DB = new SQLiteConnection(@"Data Source="+DBFileName);
DB.Open();
SQLiteCommand command = new SQLiteCommand("PRAGMA table_info('tracks')", DB);
DataTable dataTable = new DataTable();
SQLiteDataAdapter dataAdapter = new SQLiteDataAdapter(command);
dataAdapter.Fill(dataTable);
DB.Close();
foreach (DataRow row in dataTable.Rows) { 
    DBColumnNames.Add((string)row[dataTable.Columns[1]]); }  
            //Out(String.Join(",", 
    DBColumnNames.ToArray()));//debug

All elements in the resulted rows:
int cid, string name, string type,int notnull, string dflt_value, int pk

More info on PRAGMA

Answer 3

Not sure if this exactly what you are after but this is how I have grabbed the data and subsequently used it. Hope it helps! Obviously the switch is not covering all eventualities, just those I have needed to so far.

    /// <summary>
    ///  Allows the programmer to easily update rows in the DB.
    /// </summary>
    /// <param name="tableName">The table to update.</param>
    /// <param name="data">A dictionary containing Column names and their new values.</param>
    /// <param name="where">The where clause for the update statement.</param>
    /// <returns>A boolean true or false to signify success or failure.</returns>
    public bool Update(String tableName, Dictionary<String, String> data, String where)
    {
        String vals = "";
        Boolean returnCode = true;

        //Need to determine the dataype of fields to update as this affects the way the sql needs to be formatted
        String colQuery = "PRAGMA table_info(" + tableName + ")";
        DataTable colDataTypes = GetDataTable(colQuery);


        if (data.Count >= 1)
        {

            foreach (KeyValuePair<String, String> pair in data)
            {

                DataRow[] colDataTypeRow = colDataTypes.Select("name = '" + pair.Key.ToString() + "'");

                String colDataType="";
                if (pair.Key.ToString()== "rowid" || pair.Key.ToString()== "_rowid_" || pair.Key.ToString()=="oid")
                {
                    colDataType = "INT";
                }
                else
                {
                    colDataType = colDataTypeRow[0]["type"].ToString();

                }
                colDataType = colDataType.Split(' ').FirstOrDefault();
                if ( colDataType == "VARCHAR")
                {
                    colDataType = "VARCHAR";
                }

                switch(colDataType)
                {
                    case "INTEGER": case "INT": case "NUMERIC": case "REAL":
                            vals += String.Format(" {0} = {1},", pair.Key.ToString(), pair.Value.ToString());
                            break;
                    case "TEXT": case "VARCHAR": case "DATE": case "DATETIME":
                            vals += String.Format(" {0} = '{1}',", pair.Key.ToString(), pair.Value.ToString());
                            break;

                }
            }
            vals = vals.Substring(0, vals.Length - 1);
        }
        try
        {
            string sql = String.Format("update {0} set {1} where {2};", tableName, vals, where);
            //dbl.AppendLine(sql);
            dbl.AppendLine(sql);
            this.ExecuteNonQuery(sql);
        }
        catch(Exception crap)
        {
            OutCrap(crap);
            returnCode = false;
        }
        return returnCode;
    }