all data is not being read from excel file

I am using the code below to read data from a excel sheet and add the data into a data sheet but when reading the file and inspecting the data in the data-table some of the data is missing.. I have been looking at this and have no idea why this would be the case.

excelConnectionString =
                  "Provider=Microsoft.ACE.OLEDB.12.0;Data Source=" + fileName +
                      " ;Extended Properties=Excel 12.0";
            try
            {
                // Create Connection to Excel Workbook
                using (OleDbConnection connection =
                new OleDbConnection(excelConnectionString))
                {
                    connection.Open();
                    System.Data.DataTable dt = connection.GetOleDbSchemaTable(OleDbSchemaGuid.Tables, null);
                    string[] excelSheet = new String[dt.Rows.Count];
                    int sheet = 0;
                    foreach (DataRow row in dt.Rows)
                    {
                        excelSheet[sheet] = row["Table_Name"].ToString();
                        sheet++;

                    }
                    for (int i = 0; i < excelSheet.Length; i++)
                    {
                        OleDbCommand command = new OleDbCommand
                             ("Select  * FROM [" + excelSheet[i] + "]", connection);

                        adapter.SelectCommand = command;
                        adapter.Fill(dt);
                        dataGridView1.DataSource = dt;
                    }