C#

string connectionString = String.Format(@"Provider=Microsoft.ACE.OLEDB.12.0;Data Source={0};Extended Properties=""Excel 12.0;HDR=YES;IMEX=1;""", openFileDialog1.FileName);
string query = String.Format("select * from [{0}$]", SheetName);
OleDbDataAdapter dataAdapter = new OleDbDataAdapter(query, connectionString);

DataSet ds = new DataSet();

dataAdapter.Fill(ds);
dataGridView1.DataSource = ds.Tables[0];

int row = ds.Tables[0].Rows.Count;
int col = ds.Tables[0].Columns.Count;

for (int i = 0; i < row - 1; i++)
{
  dataGridView1.Rows[i].HeaderCell.Value = ds.Tables[0].Rows[i].ToString(); ;
}

for (int j = 0; j < col - 1; j++)
{
  dataGridView1.Columns[j].HeaderCell.Value = ds.Tables[0].Columns[j].ToString();
}

string username = "username";
string password = "pass";
string commit = "Login";
string postData = string.Format("txtuserid={0}&txtpassword={1}&btnlogin={2}", username, password, commit);

ASCIIEncoding enc = new ASCIIEncoding();

webBrowser1.Navigate("new page.html", "", enc.GetBytes(postData), "Content-Type: application/x-www-form-urlencoded\r\n");