oledb_create_excel.cs

var connectionString = @"Provider=Microsoft.Jet.OLEDB.4.0;Data Source=d:\\ExcelWorkBook.xls;Extended Properties=Excel 8.0";
using (var excelConnection = new OleDbConnection(connectionString))
{
    // The excel file does not need to exist, opening the connection will create the
    // excel file for you
    excelConnection.Open(); 

    // data is an object so it works with DBNull.Value
    object propertyOneValue = "cool!";
    object propertyTwoValue = "testing";

    var sqlText = "CREATE TABLE YourTableNameHere ([PropertyOne] VARCHAR(100), [PropertyTwo] VARCHAR(100))";

    // Executing this command will create the worksheet inside of the workbook
    // the table name will be the new worksheet name
    using (var command = new OleDbCommand(sqlText, excelConnection)) { command.ExecuteNonQuery(); }

    // Add (insert) data to the worksheet
    var commandText = string.Format("Insert Into YourTableNameHere ([PropertyOne], [PropertyTwo]) Values ('{0}', '{1}')", propertyOneValue, propertyTwoValue);

    using (var command = new OleDbCommand(commandText, excelConnection))
    {
        // We need to allow for nulls just like we would with
        // sql, if your data is null a DBNull.Value should be used
        // instead of null 
        command.Parameters.AddWithValue("@PropertyOne", propertyOneValue ?? DBNull.Value);
        command.Parameters.AddWithValue("@PropertyTwo", propertyTwoValue ?? DBNull.Value);

        command.ExecuteNonQuery();
    }
}