The top header of "DataGridView – Stacked Header" is not fixed in the column and scrolls.

private void Form1_Load (object sender, EventArgse)
{
    This.datatable=newDataTable();

    This.datatable.Columns.Add("a");
    This.datatable.Columns.Add("b");
    This.datatable.Columns.Add("c");
    This.datatable.Columns.Add("d");
    This.datatable.Columns.Add("e");
    This.datatable.Columns.Add("f");

    This.datatable.Rows.Add (new object[]{1,2,3,4,5,6});
    This.datatable.Rows.Add (new object[]{11, 22, 33, 44, 55, 66});

    for (inti=0; i<this.datatable.Columns.Count;i++)
    {
        string colName = this.datatable.Columns[i].ColumnName;

        DataGridViewColumn dataGridViewColumn=newDataGridViewTextBoxColumn();
        dataGridViewColumn.DataPropertyName=colName;

        string groupName;

        if(i<=2)
        {
            groupName = "first";
            dataGridViewColumn.Frozen=true;
        }
        else
        {
            groupName = "second";
            dataGridViewColumn.Frozen=false;
        }

        dataGridViewColumn.HeaderText=groupName+."+colName;

        This.dataGridView1.Columns.Add(dataGridViewColumn);
    }

    This.dataGridView1.DataSource=this.datatable;

    StackedHeaderDecorator objREnder=
        new StackedHeaderDecorator (this.dataGridView1);
}