How to import and export data in datagridview and excel file programming in C#

private void button7_Click(object sender, EventArgs e)
        {
           
 
           
                saveFileDialog1.Filter = "Solo Excel (*.xls)|*.xls";
                saveFileDialog1.FileName = "*.xls"; 
                //saveFileDialog1.InitialDirectory.
 
 
                if (saveFileDialog1.ShowDialog() == DialogResult.OK)
                {
                    try
                    {
                        System.IO.StreamWriter sw = new System.IO.StreamWriter(saveFileDialog1.FileName);
                    
                    sw.WriteLine("<?xml version='1.0'?>");
                    sw.WriteLine("<?mso-application progid='Excel.Sheet'?>");
                    sw.WriteLine("<ss:Workbook xmlns:ss='urn:schemas-microsoft-com:office:spreadsheet'>");
                    sw.WriteLine(" <ss:Styles>");
                    sw.WriteLine(" <ss:Style ss:ID='1'>");
                    sw.WriteLine(" <ss:Font ss:Bold='1'/>");
                    sw.WriteLine(" </ss:Style>");
                    sw.WriteLine(" </ss:Styles>");
                    sw.WriteLine(" <ss:Worksheet ss:Name='Sheet1'>");
                    sw.WriteLine(" <ss:Table>");
                    for (int i = 0; i < dataGridView1.Columns.Count; i++)
                    {
                        sw.WriteLine("<ss:Column ss:Width='{0}'/>", dataGridView1.Columns[i].Width);
                    }
                    sw.WriteLine("<ss:Row ss:StyleID='1'>");
 
                    for (int i = 0; i < dataGridView1.Columns.Count; i++)
                    {
                        sw.WriteLine(String.Format(("<ss:Cell>")));
 
                        sw.WriteLine(String.Format(("<ss:Data ss:Type=\"String\">{0}</ss:Data>"), (dataGridView1.Columns[i].HeaderText)));
 
                        sw.WriteLine(String.Format(("</ss:Cell>")));
 
                    }
 
                    sw.WriteLine("</ss:Row>");
 
                    for (int intFila = 0; intFila < dataGridView1.RowCount - 1; intFila++)
                    {
                        sw.WriteLine(String.Format("<ss:Row ss:Height ='{0}'>", dataGridView1.Rows[intFila].Height));
 
                        for (int intColumna = 0; intColumna < dataGridView1.Columns.Count; intColumna++)
                        {
 
                            sw.WriteLine(String.Format(("<ss:Cell>")));
 
                            sw.WriteLine(String.Format(("<ss:Data ss:Type=\"String\">{0}</ss:Data>"), (dataGridView1[intColumna, intFila].Value.ToString())));
 
                            sw.WriteLine(String.Format(("</ss:Cell>")));
 
                        }
 
                        sw.WriteLine("</ss:Row>");
 
                    }
 
                    sw.WriteLine("</ss:Table>");
 
                    sw.WriteLine("</ss:Worksheet>");
 
                    sw.WriteLine("</ss:Workbook>");
 
                    sw.Close();
 
                    MessageBox.Show("La informacion ha sido Guardada exitosamente");
                    }
                    catch (IOException)
                    {
                        MessageBox.Show("El archivo esta abierto");
                    }
                    
                }
            
                      
        }

No se controló System.Data.OleDb.OleDbException
  Message="La tabla externa no tiene el formato esperado."
  Source="Microsoft JET Database Engine"
  ErrorCode=-2147467259
  StackTrace:
       en System.Data.OleDb.OleDbConnectionInternal..ctor(OleDbConnectionString constr, OleDbConnection connection)
       en System.Data.OleDb.OleDbConnectionFactory.CreateConnection(DbConnectionOptions options, Object poolGroupProviderInfo, DbConnectionPool pool, DbConnection owningObject)
       en System.Data.ProviderBase.DbConnectionFactory.CreateNonPooledConnection(DbConnection owningConnection, DbConnectionPoolGroup poolGroup)
       en System.Data.ProviderBase.DbConnectionFactory.GetConnection(DbConnection owningConnection)
       en System.Data.ProviderBase.DbConnectionClosed.OpenConnection(DbConnection outerConnection, DbConnectionFactory connectionFactory)
       en System.Data.OleDb.OleDbConnection.Open()
       en uniwellProgram.Form1.button6_Click(Object sender, EventArgs e) en C:\Documents and Settings\Administrador\Escritorio\uniwellProgramCopia\uniwellProgram\Form1.cs:línea 235
       en System.Windows.Forms.Control.OnClick(EventArgs e)
       en System.Windows.Forms.Button.OnClick(EventArgs e)
       en System.Windows.Forms.Button.OnMouseUp(MouseEventArgs mevent)
       en System.Windows.Forms.Control.WmMouseUp(Message& m, MouseButtons button, Int32 clicks)
       en System.Windows.Forms.Control.WndProc(Message& m)
       en System.Windows.Forms.ButtonBase.WndProc(Message& m)
       en System.Windows.Forms.Button.WndProc(Message& m)
       en System.Windows.Forms.Control.ControlNativeWindow.OnMessage(Message& m)
       en System.Windows.Forms.Control.ControlNativeWindow.WndProc(Message& m)
       en System.Windows.Forms.NativeWindow.DebuggableCallback(IntPtr hWnd, Int32 msg, IntPtr wparam, IntPtr lparam)
       en System.Windows.Forms.UnsafeNativeMethods.DispatchMessageW(MSG& msg)
       en System.Windows.Forms.Application.ComponentManager.System.Windows.Forms.UnsafeNativeMethods.IMsoComponentManager.FPushMessageLoop(Int32 dwComponentID, Int32 reason, Int32 pvLoopData)
       en System.Windows.Forms.Application.ThreadContext.RunMessageLoopInner(Int32 reason, ApplicationContext context)
       en System.Windows.Forms.Application.ThreadContext.RunMessageLoop(Int32 reason, ApplicationContext context)
       en System.Windows.Forms.Application.Run(Form mainForm)
       en uniwellProgram.Program.Main() en C:\Documents and Settings\Administrador\Escritorio\uniwellProgramCopia\uniwellProgram\Program.cs:línea 17
       en System.AppDomain.nExecuteAssembly(Assembly assembly, String[] args)
       en System.AppDomain.ExecuteAssembly(String assemblyFile, Evidence assemblySecurity, String[] args)
       en Microsoft.VisualStudio.HostingProcess.HostProc.RunUsersAssembly()
       en System.Threading.ThreadHelper.ThreadStart_Context(Object state)
       en System.Threading.ExecutionContext.Run(ExecutionContext executionContext, ContextCallback callback, Object state)
       en System.Threading.ThreadHelper.ThreadStart()