Cant create NpgsqlDataAdapter with insert/update

I am trying to create a generic form which would be configurable from the XML config. That config is supposed to store the settings for NpgsqlDataAdapter, which will be used to insert/update/delete data in the form. I've created such config, but however the dataAdapter is showing errors when I am trying to insert/update msth into database. Could you please help? ERROR CODE: 42703 (Column does not exists. Hint: table contains column "key", but it cannot be refernced from this part of the query).

Here is the XML:

<Frm>
  <SelectCommand type="text">
    <text>
  SELECT * FROM npdata
    </text>
  </SelectCommand>
  <InsertCommand type="text">
    <text>
      INSERT INTO npdata VALUES (@key, @ndata)
    </text>
    <params>
      <param name="@key" column="key" type="19" sourceversion="current">              </param>
      <param name="@ndata" column="ndata" type="1" sourceversion="current">>  </param>
    </params>
   </InsertCommand>
  <UpdateCommand type="text">
    <text>
      UPDATE npdata SET key = @key, ndata = @ndata WHERE key = @key
    </text>
    <params>
      <param name="@key" column="key" type="19"  sourceversion="original">    </param>
      <param name="@ndata" column="ndata" type="1" sourceversion="current">    </param>
    </params>
  </UpdateCommand>
  <DeleteCommand type="text">
    <text>
      DELETE FROM npdata WHERE key = @key
    </text>
    <params>
      <param name="@key" column="key" type="19" sourceversion="original">        </param>
    </params>
  </DeleteCommand>
</Frm>

And this is the code behing for the form:

string txt;
        string _pname;
        NpgsqlTypes.NpgsqlDbType _type;
        string _colname;

        conn = new NpgsqlConnection(@"Server=localhost;Port=5432;Database=npgsqldata_test;UserId=postgres;Password=postgres;TIMEOUT=120");

        using (var cmd = new NpgsqlCommand("SELECT xml FROM npsettings", conn))
        {

            if (cmd.Connection.State != ConnectionState.Open)
            {
                conn.Open();
            }

            txt = cmd.ExecuteScalar().ToString();
        }

        XDocument doc = XDocument.Parse(txt);

        dset = new DataSet("npdata");

        NpAdapter = new NpgsqlDataAdapter();

        string _selcmd = doc.Root.Element("SelectCommand").Value;

        NpAdapter.SelectCommand = new NpgsqlCommand(_selcmd, conn);

        if (doc.Root.Element("SelectCommand").Attribute("type").Value.ToLower() == ("Procedure").ToLower())
        {
            NpAdapter.SelectCommand.CommandType = CommandType.StoredProcedure;
        }

        NpAdapter.Fill(dset, "npdata");
        dtsource = dset.Tables["npdata"];

        string _delcommand = doc.Root.Element("DeleteCommand").Element("text").Value;

        if (!String.IsNullOrEmpty(_delcommand))
        {
            NpAdapter.DeleteCommand = new NpgsqlCommand(_delcommand, conn);

            foreach (var c in doc.Root.Element("DeleteCommand").Element("params").Elements())
            {
                _pname = c.Attribute("name").Value;
                _type = (NpgsqlTypes.NpgsqlDbType)c.Attribute("type").Value.NToInt32();
                _colname = c.Attribute("column").Value;

                NpParam = NpAdapter.DeleteCommand.Parameters.Add(_pname, _type);
                NpParam.SourceColumn = _colname;

                if (c.Attribute("sourceversion").Value == "original")
                {
                    NpParam.SourceVersion = DataRowVersion.Original;
                }
                else
                {
                    NpParam.SourceVersion = DataRowVersion.Current;
                }

            }

            if (doc.Root.Element("DeleteCommand").Attribute("type").Value.ToLower() == ("Procedure").ToLower())
            {
                NpAdapter.SelectCommand.CommandType = CommandType.StoredProcedure;
            }
        }

        string _inscommand = doc.Root.Element("InsertCommand").Element("text").Value;

        if (!String.IsNullOrEmpty(_inscommand))
        {
            NpAdapter.InsertCommand = new NpgsqlCommand(_inscommand, conn);

            foreach (var c in doc.Root.Element("InsertCommand").Element("params").Elements())
            {
                _pname = c.Attribute("name").Value;
                _type = (NpgsqlTypes.NpgsqlDbType)c.Attribute("type").Value.NToInt32();
                _colname = c.Attribute("column").Value;

                NpParam = NpAdapter.DeleteCommand.Parameters.Add(_pname, _type);
                NpParam.SourceColumn = _colname;

                if (c.Attribute("sourceversion").Value == "original")
                {
                    NpParam.SourceVersion = DataRowVersion.Original;
                }
                else
                {
                    NpParam.SourceVersion = DataRowVersion.Current;
                }

            }

            if (doc.Root.Element("InsertCommand").Attribute("type").Value.ToLower() == ("Procedure").ToLower())
            {
                NpAdapter.SelectCommand.CommandType = CommandType.StoredProcedure;
            }
        }

        string _updcommand = doc.Root.Element("UpdateCommand").Element("text").Value;

        if (!String.IsNullOrEmpty(_updcommand))
        {
            NpAdapter.UpdateCommand = new NpgsqlCommand(_inscommand, conn);

            foreach (var c in doc.Root.Element("UpdateCommand").Element("params").Elements())
            {
                _pname = c.Attribute("name").Value;
                _type = (NpgsqlTypes.NpgsqlDbType)c.Attribute("type").Value.NToInt32();
                _colname = c.Attribute("column").Value;

                NpParam = NpAdapter.DeleteCommand.Parameters.Add(_pname, _type);
                NpParam.SourceColumn = _colname;

                if (c.Attribute("sourceversion").Value == "original")
                {
                    NpParam.SourceVersion = DataRowVersion.Original;
                }
                else
                {
                    NpParam.SourceVersion = DataRowVersion.Current;
                }
            }

            if (doc.Root.Element("UpdateCommand").Attribute("type").Value.ToLower() == ("Procedure").ToLower())
            {
                NpAdapter.SelectCommand.CommandType = CommandType.StoredProcedure;
            }
        }

        dataGridView1.DataSource = dset.Tables["npdata"];
        dtsource.RowChanged += (ss, ee) => { MessageBox.Show("changed"); };