This blog describes how to convert .NET Data Provider for Teradata Learning Examples from C# to VB or C++.
.NET Data Provider for Teradata product installs Learning Examples in "<.NET Data Provider Installation Directory>\samples\LearningExamples" directory (e.g. "C:\Program Files\Teradata\NET Data Provider for Teradata\13.01.00\samples\LearningExamples"). These samples are written in C# language and we will ship VB samples some time in future.
But there is an easy way to convert the C# samples to VB as outlined below:
Download and install ".NET Reflector" from http://www.red-gate.com/products/dotnet-development/reflector/.
Compile one C# sample; see "<.NET Data Provider Installation Directory>\ samples\LearningExamples\Readme.doc" for details.
Use ".NET Reflector" to open the resulting executable.
Find the "Main(String[]): Void" method; right click and select Disassemble.
Select "Visual Basic", "C#" or "MC++" from the toolbar.
For example I used the above procedure to convert:
static void Main(string[] args)
{
try
{
System.Console.WriteLine("Sample T20303TD: \n");
System.Console.WriteLine(" Looking for .NET Data Provider for Teradata...");
// Attempting to connect to Teradata
System.Console.WriteLine(" Attempting to open a connection to Teradata via " +
"the .NET Data Provider... \n");
// Create a TdConnection object. A Connection
// represents a session with a specific database. Within the context
// of a Connection, SQL commands are executed and results are returned.
// Creating and opening a database connection with the given connection string.
TdConnection con = new TdConnection(Constants.sConnection);
con.Open();
System.Console.WriteLine(" User " + Constants.sUser + " connected.");
System.Console.WriteLine(" Connection to Teradata established. \n");
try
{
// Create a TdCommand object. A command object executes
// SQL commands on a specified Connection. In order to specify which
// connection, set its connection property. Command.ExecuteReader will return
// a TdDataReader which is used to read the result of a SQL command.
// Command.ExecuteNonQuery will perform the specified SQL command but
// will not return a reader.
TdCommand cmd = con.CreateCommand();
try
{
// The following code will perform a SELECT query
// on the table.
cmd.CommandText = Constants.sSelect;
TdParameter par1 = cmd.CreateParameter();
par1.Value = Constants.sDept;
par1.ParameterName = "Dept";
par1.DbType = DbType.String;
par1.Size = Constants.sDept.Length;
cmd.Parameters.Add(par1);
// ExecuteReader method is being used without passing the SchemaOnly
// behavior because access to the ResultSet data is required
TdDataReader reader = cmd.ExecuteReader();
try
{
// Display result set table column meta data
displayRSMetaData(reader);
System.Console.WriteLine("\n\n Using ExecuteReader() to execute the following" +
" SQL command: \n\n");
System.Console.WriteLine(Constants.sSelect + '\n');
// Extract and display result set table data
System.Console.WriteLine();
System.Console.WriteLine(" DISPLAYING RESULT SET DATA:");
System.Console.WriteLine(" ---------------------------");
int rowCount = 0; // result set row counter
// If there are rows iterate through all returned values and display them
if (reader.HasRows)
{
// While there is more to read
while (reader.Read())
{
rowCount++; // increment retrieved row counter
// Extract column values
String name = reader.GetString(0);
int id = reader.GetInt32(1);
// Geting BLOB
String bFilename = Environment.CurrentDirectory + @"\output\" + id + ".jpg";
// Create a filestream to output BLOB to
FileStream fs = new FileStream(bFilename, FileMode.Create, FileAccess.Write);
try
{
// Create a buffer
Byte[] bBuffer = new byte[100];
// Call reader.GetTdBlob which will return a TdBlob.
// TdBlobs support chunking so bytes can be read incrementally.
TdBlob blob = reader.GetTdBlob(3);
long numOfBytes;
do
{
// Fill the buffer with bytes from the reader
numOfBytes = blob.Read(bBuffer, 0, Constants.BUFFERSIZE);
// Write bytes to the filestream
fs.Write(bBuffer, 0, Constants.BUFFERSIZE);
} while (numOfBytes == Constants.BUFFERSIZE);
// The last segment of bytes will not fill the entire buffer
// so we will continue while the number of bytes read fill the
// entire buffer.
}
finally
{
fs.Close();
}
String cFilename = Environment.CurrentDirectory + @"\output\" + id + ".txt";
// Create a filestream to output CLOB to
StreamWriter sw = File.CreateText(cFilename);
// Geting CLOB
try
{
// Create a buffer
Char[] cBuffer = new char[100];
// Call reader.GetTdClob which will return a TdClob.
// TdClobs support chunking so chars can be read incrementally.
TdClob clob = reader.GetTdClob(2);
long numOfChars;
do
{
// Fill the buffer with chars from the reader
numOfChars = clob.Read(cBuffer, 0, Constants.BUFFERSIZE);
// Write bytes to the filestream
sw.Write(cBuffer, 0, Constants.BUFFERSIZE);
} while (numOfChars == Constants.BUFFERSIZE);
// The last segment of chars will not fill the entire buffer
// so we will continue while the number of chars read fill the
// entire buffer.
}
finally
{
sw.Close();
}
// get the interval data
TdIntervalYear service = TdIntervalYear.Parse(reader.GetString(4));
TdIntervalDay workdays = TdIntervalDay.Parse(reader.GetString(5));
System.Console.WriteLine("\n ROW " + rowCount);
System.Console.WriteLine(" ----------");
System.Console.WriteLine(" COLUMN empName : " + name);
System.Console.WriteLine(" COLUMN empID : " + id);
System.Console.WriteLine(" COLUMN empResume : Resume saved as " + cFilename);
System.Console.WriteLine(" COLUMN empPhoto : Photo saved as " + bFilename);
System.Console.WriteLine(" COLUMN empService : " + service.ToString());
System.Console.WriteLine(" COLUMN empWorkDays : " + workdays.ToString());
}
}
System.Console.WriteLine("\n " + reader.RecordsReturned + " Row(s) retrieved. \n");
}
finally
{
reader.Close();
}
}
finally
{
cmd.Dispose();
System.Console.WriteLine(" Command Disposed. \n");
}
}
finally
{
// Close the connection
System.Console.WriteLine(" Closing connection to Teradata...");
con.Close();
System.Console.WriteLine(" Connection to Teradata closed. \n");
}
System.Console.WriteLine(" Sample T20303TD finished. \n");
}
catch (DbException ex)
{
// A DbException was generated. Catch it and display
// the error information.
// Note that there could be multiple error objects chained
// together.
if (ex is TdException)
{
foreach (TdError err in ((TdException)ex).Errors)
{
System.Console.WriteLine(err.Message);
}
}
System.Console.WriteLine(ex.Message);
System.Console.WriteLine("*** DbException caught ***");
}
catch (Exception ex)
{
// An exception of some other type has been generated.
// Display the error information.
System.Console.WriteLine(ex.Message);
System.Console.WriteLine(ex.StackTrace);
}
}
to
Private Shared Sub Main(ByVal args As String())
Try
Console.WriteLine("Sample T20303TD: "& ChrW(10))
Console.WriteLine(" Looking for .NET Data Provider for Teradata...")
Console.WriteLine(" Attempting to open a connection to Teradata via the .NET Data Provider... "& ChrW(10))
Dim con As New TdConnection(Constants.sConnection)
con.Open
Console.WriteLine((" User "& Constants.sUser & " connected."))
Console.WriteLine(" Connection to Teradata established. "& ChrW(10))
Try
Dim cmd As TdCommand = con.CreateCommand
Try
cmd.CommandText = Constants.sSelect
Dim par1 As TdParameter = cmd.CreateParameter
par1.Value = Constants.sDept
par1.ParameterName = "Dept" par1.DbType = DbType.String
par1.Size = Constants.sDept.Length
cmd.Parameters.Add(par1)
Dim reader As TdDataReader = cmd.ExecuteReader
Try
T20303TD.displayRSMetaData(reader)
Console.WriteLine(ChrW(10) & ChrW(10) & " Using ExecuteReader() to execute the following SQL command: "& ChrW(10) & ChrW(10))
Console.WriteLine((Constants.sSelect & ChrW(10)))
Console.WriteLine
Console.WriteLine(" DISPLAYING RESULT SET DATA:")
Console.WriteLine(" ---------------------------")
Dim rowCount As Integer = 0
If reader.HasRows Then
Do While reader.Read
rowCount += 1
Dim name As String = reader.GetString(0)
Dim id As Integer = reader.GetInt32(1)
Dim bFilename As String = String.Concat(New Object() { Environment.CurrentDirectory, "\output\", id, ".jpg" })
Dim fs As New FileStream(bFilename, FileMode.Create, FileAccess.Write)
Try
Dim numOfBytes As Long
Dim bBuffer As Byte() = New Byte(100 - 1) {}
Dim blob As TdBlob = reader.GetTdBlob(3)
Do
numOfBytes = blob.Read(bBuffer, 0, Constants.BUFFERSIZE)
fs.Write(bBuffer, 0, Constants.BUFFERSIZE)
Loop While (numOfBytes = Constants.BUFFERSIZE)
Finally
fs.Close
End Try
Dim cFilename As String = String.Concat(New Object() { Environment.CurrentDirectory, "\output\", id, ".txt" })
Dim sw As StreamWriter = File.CreateText(cFilename)
Try
Dim numOfChars As Long
Dim cBuffer As Char() = New Char(100 - 1) {}
Dim clob As TdClob = reader.GetTdClob(2)
Do
numOfChars = clob.Read(cBuffer, 0, Constants.BUFFERSIZE)
sw.Write(cBuffer, 0, Constants.BUFFERSIZE)
Loop While (numOfChars = Constants.BUFFERSIZE)
Finally
sw.Close
End Try
Dim service As TdIntervalYear = TdIntervalYear.Parse(reader.GetString(4))
Dim workdays As TdIntervalDay = TdIntervalDay.Parse(reader.GetString(5))
Console.WriteLine((ChrW(10) & " ROW "& rowCount))
Console.WriteLine(" ----------")
Console.WriteLine((" COLUMN empName : "& name))
Console.WriteLine((" COLUMN empID : "& id))
Console.WriteLine((" COLUMN empResume : Resume saved as "& cFilename))
Console.WriteLine((" COLUMN empPhoto : Photo saved as "& bFilename))
Console.WriteLine((" COLUMN empService : "& service.ToString))
Console.WriteLine((" COLUMN empWorkDays : "& workdays.ToString))
Loop
End If
Console.WriteLine((ChrW(10) & ""& reader.RecordsReturned & " Row(s) retrieved. "& ChrW(10)))
Finally
reader.Close
End Try
Finally
cmd.Dispose
Console.WriteLine(" Command Disposed. "& ChrW(10))
End Try
Finally
Console.WriteLine(" Closing connection to Teradata...")
con.Close
Console.WriteLine(" Connection to Teradata closed. "& ChrW(10))
End Try
Console.WriteLine(" Sample T20303TD finished. "& ChrW(10))
Catch ex As DbException
If TypeOf ex Is TdException Then
Dim err As TdError
For Each err In DirectCast(ex, TdException).Errors
Console.WriteLine(err.Message)
Next
End If
Console.WriteLine(ex.Message)
Console.WriteLine("*** DbException caught ***")
Catch ex As Exception
Console.WriteLine(ex.Message)
Console.WriteLine(ex.StackTrace)
End Try
End Sub
There are alternative methods of converting C# to VB; for example: http://msdn.microsoft.com/en-us/magazine/cc163652.aspx
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