Array IndexOutOfRangeException on MySQL Connection String in ASP.NET

I’m currently using the ASP.NET framework to build a website that can send information to a MySQL database hosted on PHPMyAdmin. The data being read into the database comes from a CSV file that the user uploads to the website. So far, the following code has worked successfully on smaller sample files (variable names changed and sensitive information hidden):

string connectionString = "Server=****;Database=****;Uid=****;Pwd=****";

                using (MySqlConnection connection = new MySqlConnection(connectionString))
                {
                    connection.Open();

                    using (MySqlCommand command = connection.CreateCommand())
                    {
                        command.CommandType = CommandType.Text;

                        // clear the table before inserting new data:
                        command.CommandText = "DELETE FROM CustomerData";
                        command.ExecuteNonQuery();

                        // read the CSV file and insert data into the table:
                        using (StreamReader reader = new StreamReader(fileName))
                        {
                            string line;
                            bool isFirstLine = true;
                            while ((line = reader.ReadLine()) != null)
                            {
                                if (isFirstLine)
                                {
                                    isFirstLine = false;
                                    continue; // skip the first line
                                }

                                string[] values = line.Split(',');

                                // prepare the SQL insert statement:
                                // prepare the SQL insert statement:
                                command.CommandText = "INSERT INTO CustomerData (Data1, Data2, Data3, Data4, Data5, Data6, Data7, Data8, Data9, Data10, Data11, Data12, Data13, Data14, Data15, Data16, Data17, Data18, Data19, Data20, Data21, Data22, Data23, Data24, Data25, Data26) " +
                                                    "VALUES (@Data1, @Data2, @Data3, @Data4, @Data5, @Data6, @Data7, @Data8, @Data9, @Data10, @Data11, @Data12, @Data13, @Data14, @Data15, @Data16, @Data17, @Data18, @Data19, @Data20, @Data21, @Data22, @Data23, @Data24, @Data25, @Data26)";

                                // set parameter values, accounting for possible nulls:
                                command.Parameters.Clear();

                                command.Parameters.AddWithValue("@Data1", string.IsNullOrEmpty(values[0]) ? DBNull.Value : values[0]);
                                command.Parameters.AddWithValue("@Data2", string.IsNullOrEmpty(values[1]) ? DBNull.Value : (object)values[1]);
                                command.Parameters.AddWithValue("@Data3", string.IsNullOrEmpty(values[2]) ? DBNull.Value : (object)values[2]);
                                command.Parameters.AddWithValue("@Data4", string.IsNullOrEmpty(values[3]) ? DBNull.Value : (object)values[3]);
                                command.Parameters.AddWithValue("@Data5", string.IsNullOrEmpty(values[4]) ? DBNull.Value : (object)values[4]);
                                command.Parameters.AddWithValue("@Data6", string.IsNullOrEmpty(values[5]) ? DBNull.Value : (object)values[5]);
                                command.Parameters.AddWithValue("@Data7", string.IsNullOrEmpty(values[6]) ? DBNull.Value : (object)values[6]);
                                command.Parameters.AddWithValue("@Data8", string.IsNullOrEmpty(values[7]) ? DBNull.Value : (object)values[7]);
                                command.Parameters.AddWithValue("@Data9", string.IsNullOrEmpty(values[8]) ? DBNull.Value : (object)values[8]);
                                command.Parameters.AddWithValue("@Data10", string.IsNullOrEmpty(values[9]) ? DBNull.Value : (object)values[9]);
                                command.Parameters.AddWithValue("@Data11", string.IsNullOrEmpty(values[10]) ? DBNull.Value : (object)values[10]);
                                command.Parameters.AddWithValue("@Data12", string.IsNullOrEmpty(values[11]) ? DBNull.Value : (object)values[11]);
                                command.Parameters.AddWithValue("@Data13", string.IsNullOrEmpty(values[12]) ? DBNull.Value : (object)values[12]);
                                command.Parameters.AddWithValue("@Data14", string.IsNullOrEmpty(values[13]) ? DBNull.Value : (object)values[13]);
                                command.Parameters.AddWithValue("@Data15", string.IsNullOrEmpty(values[14]) ? DBNull.Value : (object)values[14]);
                                command.Parameters.AddWithValue("@Data16", string.IsNullOrEmpty(values[15]) ? DBNull.Value : (object)values[15]);
                                command.Parameters.AddWithValue("@Data17", string.IsNullOrEmpty(values[16]) ? DBNull.Value : (object)values[16]);
                                command.Parameters.AddWithValue("@Data18", string.IsNullOrEmpty(values[17]) ? DBNull.Value : (object)values[17]);
                                command.Parameters.AddWithValue("@Data19", string.IsNullOrEmpty(values[18]) ? DBNull.Value : (object)values[18]);
                                command.Parameters.AddWithValue("@Data20", string.IsNullOrEmpty(values[19]) ? DBNull.Value : (object)values[19]);
                                command.Parameters.AddWithValue("@Data21", string.IsNullOrEmpty(values[20]) ? DBNull.Value : (object)values[20]);
                                command.Parameters.AddWithValue("@Data22", string.IsNullOrEmpty(values[21]) ? DBNull.Value : (object)values[21]);
                                command.Parameters.AddWithValue("@Data23", string.IsNullOrEmpty(values[22]) ? DBNull.Value : (object)values[22]);
                                command.Parameters.AddWithValue("@Data24", string.IsNullOrEmpty(values[23]) ? DBNull.Value : (object)values[23]);
                                command.Parameters.AddWithValue("@Data25", string.IsNullOrEmpty(values[24]) ? DBNull.Value : (object)values[24]);
                                command.Parameters.AddWithValue("@Data26", string.IsNullOrEmpty(values[25]) ? DBNull.Value : (object)values[25]);


                                // execute the insert statement:
                                command.ExecuteNonQuery();
                            }
                        }
                    }
                }

As stated, this code 100% worked when I was trying to upload smaller CSV files to the MySQL database. However, when I began trying to upload CSV files that have upwards of 25,000 lines, I would receive the following error:

System.IndexOutOfRangeException: Index was outside the bounds of the
array.

And it was occurring on the line with my connection string:

string connectionString = "Server=****;Database=****;Uid=****;Pwd=****";

Suffice it to say that this error has left me quite baffled. I’m not even sure how that specific error could be occurring on the line in question. I realize it must have something to do with the way the MySQL database is receiving the information from the CSV file, but I don’t know how to go about resolving this. Any help/advice is greatly appreciated!