first things first, my program is supposed to append the contents of a CSV file to an SQL table in SQL Server, using the path put into a text box "pathInputTextBox" and table name from a text box "tableInputTextBox" when you press the button "toSqlButton". After I'm done with this part I will also have it do so for different types of data bases using different buttons, but for now it already fails at reading the csv file. (I don't even know if it can even correctly append the data afterwards, but I am a silly lad that writes all of the code first and then tackles one problem after another, so I'll cross that bridge when I get there.)
The error is:
CsvHelper.ReaderException: 'No header record was found.
IReader state:
ColumnCount: 0
CurrentIndex: -1
HeaderRecord:
from the line
csv.ReadHeader();
in the toSQLButton_Click event. By debugging I have found out that this is due to the method ReadCSV returning null, as it should whenever reading the file fails.
Among some of the things I have tried to fix this are writing different ways to read the file (e.g. TextReader) that would still work with a similar syntax and writing
CsvReader csv = new CsvReader(reader, new CsvConfiguration(CultureInfo.InvariantCulture) {Delimiter = ";", HasHeaderRecord = true });
instead of
CsvReader csv = new CsvReader(reader, CultureInfo.InvariantCulture);
but none of that seems to work. I am 100% sure that the file path I write into the Text Box should work (yes, I deleted the "s after copying it in the file explorer). I have sifted through the internet and asked ChatGPT for help but I am at my wits ends and it feels like it must be some very tiny, silly rookie mistake baked into the code somewhere that should be obvious. Please help me, I am looking forward to your responses.
The code:
private CsvReader ReadCSV(string pathString)
{
try
{
var reader = new StreamReader(pathString);
CsvReader csv = new CsvReader(reader, new CsvConfiguration(CultureInfo.InvariantCulture) { Delimiter = ";", HasHeaderRecord = true });
return csv;
}
catch (FileNotFoundException)
{
MessageBox.Show("File not found. Please check the entered file path.", "Error", MessageBoxButtons.OK, MessageBoxIcon.Error);
}
catch (Exception ex)
{
MessageBox.Show("An error occurred while reading the CSV file: " + ex.Message, "Error", MessageBoxButtons.OK, MessageBoxIcon.Error);
}
return null;
}
private void toSqlButton_Click(object sender, EventArgs e)
{
string sqlConnection = "Data Source=VERYCOOLDATASOURCE\\SQLEXPRESS;Initial Catalog=VeryCoolDB;Integrated Security=True";
CsvReader csv = ReadCSV(pathInputTextBox.Text);
using(SqlConnection sqlconn = new SqlConnection(sqlConnection))
{
// Get CSV column names for comparison
csv.ReadHeader();
List<string> csvColumns = csv.HeaderRecord.ToList() ?? new List<string>();
// Get SQL column names for comparison
List<string> sqlColumns = GetSQLColumns(sqlConnection, $"SELECT COLUMN_NAME FROM INFORMATION_SCHEMA.COLUMNS WHERE TABLE_NAME = '{tableInputTextBox.Text}'");
// Compare columns
if (csvColumns.All(sqlColumns.Contains) && csvColumns.Count == sqlColumns.Count)
{
try
{
sqlconn.Open();
using (SqlTransaction sqltrans = sqlconn.BeginTransaction())
using (SqlBulkCopy sqlcopy = new SqlBulkCopy(sqlconn, SqlBulkCopyOptions.KeepIdentity, sqltrans))
{
sqlcopy.DestinationTableName = tableInputTextBox.Text;
CsvDataReader csvdata = new CsvDataReader(csv);
sqlcopy.WriteToServer(csvdata);
sqltrans.Commit();
}
sqlconn.Close();
}
catch (Exception ex)
{
MessageBox.Show("An error occurred while writing the data: " + ex.Message, "Error", MessageBoxButtons.OK, MessageBoxIcon.Error);
}
}
else
{
MessageBox.Show("Columns of the CSV file and columns of the SQL table do not match.", "Error", MessageBoxButtons.OK, MessageBoxIcon.Error);
}
}
}
static List<string> GetSQLColumns(string connectionString, string query)
{
List<string> columns = new List<string>();
using (SqlConnection connection = new SqlConnection(connectionString))
{
SqlCommand command = new SqlCommand(query, connection);
connection.Open();
SqlDataReader reader = command.ExecuteReader();
while (reader.Read())
{
columns.Add(reader["COLUMN_NAME"].ToString());
}
reader.Close();
connection.Close();
}
return columns;
}
The contents of the CSV file:
mitid; vname; nname; gehalt; geburtsdatum
5; bingus; bongus; 1223.23; 2010-01-01;
6; bongus; bingus; 1223.23; 2010-01-01;
Using the file path:
C:\Users\MALA\Desktop\AppendExcelTest.csv
Thank you @Ralf for helping me realise the problem in the comments!
The problem is that when using CsvHelper, you first need to have .Read() before .ReadHeader().
According to the documentation you have to call Read before calling ReadHeader to position the CsvReader on something. See
https://joshclose.github.io/CsvHelper/getting-started/#reading-a-csv-file "Read will advance row. ReadHeader will read the row into CsvHelper as the header values. Separating Read and ReadHeader allows you to do other things with the header row before moving onto the next row."
Silly me thought, that it would automatically read the file when configuring CsvReader, probably fooled by the namesake. But you have to of course read a line first by using .Read()
Here is the corrected code (all I did was add the line
csv.Read();
before
csv.ReadHeader();
)
private CsvReader ReadCSV(string pathString)
{
try
{
var reader = new StreamReader(pathString);
CsvReader csv = new CsvReader(reader, new CsvConfiguration(CultureInfo.InvariantCulture) { Delimiter = ";", HasHeaderRecord = true });
return csv;
}
catch (FileNotFoundException)
{
MessageBox.Show("File not found. Please check the entered file path.", "Error", MessageBoxButtons.OK, MessageBoxIcon.Error);
}
catch (Exception ex)
{
MessageBox.Show("An error occurred while reading the CSV file: " + ex.Message, "Error", MessageBoxButtons.OK, MessageBoxIcon.Error);
}
return null;
}
private void toSqlButton_Click(object sender, EventArgs e)
{
string sqlConnection = "Data Source=VERYCOOLDATASOURCE\\SQLEXPRESS;Initial Catalog=VeryCoolDB;Integrated Security=True";
CsvReader csv = ReadCSV(pathInputTextBox.Text);
using(SqlConnection sqlconn = new SqlConnection(sqlConnection))
{
// Get CSV column names for comparison
csv.Read();
csv.ReadHeader();
List<string> csvColumns = csv.HeaderRecord.ToList() ?? new List<string>();
// Get SQL column names for comparison
List<string> sqlColumns = GetSQLColumns(sqlConnection, $"SELECT COLUMN_NAME FROM INFORMATION_SCHEMA.COLUMNS WHERE TABLE_NAME = '{tableInputTextBox.Text}'");
// Compare columns
if (csvColumns.All(sqlColumns.Contains) && csvColumns.Count == sqlColumns.Count)
{
try
{
sqlconn.Open();
using (SqlTransaction sqltrans = sqlconn.BeginTransaction())
using (SqlBulkCopy sqlcopy = new SqlBulkCopy(sqlconn, SqlBulkCopyOptions.KeepIdentity, sqltrans))
{
sqlcopy.DestinationTableName = tableInputTextBox.Text;
CsvDataReader csvdata = new CsvDataReader(csv);
sqlcopy.WriteToServer(csvdata);
sqltrans.Commit();
}
sqlconn.Close();
}
catch (Exception ex)
{
MessageBox.Show("An error occurred while writing the data: " + ex.Message, "Error", MessageBoxButtons.OK, MessageBoxIcon.Error);
}
}
else
{
MessageBox.Show("Columns of the CSV file and columns of the SQL table do not match.", "Error", MessageBoxButtons.OK, MessageBoxIcon.Error);
}
}
}
static List<string> GetSQLColumns(string connectionString, string query)
{
List<string> columns = new List<string>();
using (SqlConnection connection = new SqlConnection(connectionString))
{
SqlCommand command = new SqlCommand(query, connection);
connection.Open();
SqlDataReader reader = command.ExecuteReader();
while (reader.Read())
{
columns.Add(reader["COLUMN_NAME"].ToString());
}
reader.Close();
connection.Close();
}
return columns;
}