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System.Data.OracleClient Namespace | MSDN[^]:

The types in System.Data.OracleClient are deprecated and will be removed in a future version of the .NET Framework.

• Official Oracle ODP.NET, Managed Driver[^]
• Official Oracle ODP.NET, Managed Entity Framework Driver[^]

Using lob As OracleLob = reader.GetOracleLob(0)
    Using sr As New StreamReader(lob, Text.Encoding.Unicode) ' <-- You might need to adjust this
        retval = sr.Read(outChar, 0, bufferSize)
        Do Until retval = 0
            myxml.WriteRaw(outChar, 0, retval)
            myxml.Flush()
            
            Array.Clear(outChar, 0, retval)
            retval = sr.Read(outChar, 0, bufferSize)
        Loop
    End Using
End Using

1. The GetChars method creates a new OracleLob on each call, and reads its Value property.
2. The Value property reads the entire string into memory on each call.
3. The GetChars method then copies the string to a Char array.
4. The GetChars method then copies the specified section of the array to the buffer you've passed in.

Richard Deeming wrote:

EDIT: Looking at the code in dotPeek, this will be much more efficient
than calling GetChars:

Bastard Programmer from Hell
If you can't read my code, try converting it here[^]

// OracleDataReader.GetChars:
public override long GetChars(int i, long fieldOffset, char[] buffer2, int bufferoffset, int length)
{
    // Pre-condition checks omitted
    return this._columnInfo[i].GetChars(this._buffer, fieldOffset, buffer2, bufferoffset, length);
}

// OracleColumn.GetChars:
internal long GetChars(NativeBuffer_RowBuffer buffer, long fieldOffset, char[] destinationBuffer, int destinationOffset, int length)
{
    // Pre-condition checks omitted
    
    int result;
    if (this.IsLob)
    {
        // The OP said it's a CLOB column, so we're in this branch.
        using (OracleLob oracleLob = new OracleLob(this._lobLocator))
        {
            string str = (string) oracleLob.Value;
            int length1 = str.Length;
            int startIndex = (int)fieldOffset;
            result = length1 - startIndex;
            if (destinationBuffer != null)
            {
                result = Math.Min(result, length);
                if (0 < result) Buffer.BlockCopy(str.ToCharArray(startIndex, result), 0, destinationBuffer, destinationOffset, result);
            }
        }
    }
    else
    {
        // Omitted
    }
    
    return (long) Math.Max(0, result);
}

// OracleLob.Value:
public object Value
{
    get
    {
        // Pre-condition checks omitted
        
        long num = this._currentPosition;
        try
        {
            this.Seek(0L, SeekOrigin.Begin);
            if (this._lobType == OracleType.Blob || this._lobType == OracleType.BFile)
            {
                // Code to read and return a byte array omitted, since we're read a CLOB.
            }
            
            return new StreamReader(this, Encoding.Unicode).ReadToEnd();
        }
        finally
        {
            this._currentPosition = num;
        }
    }
}

1. The OracleLob.Value property reads the entire CLOB value into memory as a string;
2. The OracleColumn.GetChars method calls ToCharArray which copies (a portion of) the string to a new array;
3. It then uses Buffer.BlockCopy to copy the characters from the new array to the destinationBuffer array;

' Get the current Date/Time in a variable we can manpulate consistently
' This is because each call to DateTime.Now or DateTime.Today will return
' a different time, and if executed at midnight, different days!
Dim baseDate As DateTime = DateTime.Today()

' Build a start date based on the current month and year.
Dim startDate As DateTime = New DateTime(baseDate.Year, baseDate.Month, 1, 0, 0, 0, 0)

' Build a end date based on the current month and year.
' Add a month to the current DateTime to easier get the end date.
' This also accounts for rolling over the year.
baseDate = baseDate.AddMonth(1)
Dim stopDate = New DateTime(baseDate.Year, baseDate.Month, 1, 0, 0, 0, 0)

WHERE dateTime >= startDate AND dateTime < endDate

Dim DateStart As DateTime = DateAdd("m", -1, DateSerial(Year(Today), Month(Today), 1))
Dim DateStop As DateTime = DateAdd("m", 0, DateSerial(Year(Today), Month(Today), 0))

Dim DateStart As DateTime = DateAdd("yyyy", -1, DateSerial(Now.Year, 1, 1))
Dim DateStop As DateTime = DateAdd("yyyy", -1, DateSerial(Now.Year, 12, 31))

' Instead of:
DateSerial(year, month, day)
' use: (for valid month and day)
New DateTime(year, month, day)
' or: (for valid month, invalid day)
New DateTime(year, month, 1).AddDays(day - 1)
' or: (for invalid month and day)
New DateTime(year, 1, 1).AddMonths(month - 1).AddDays(day - 1)

' Year:
dateValue.AddYears(number)
' Quarter:
dateValue.AddMonths(number * 3)
' Month:
dateValue.AddMonths(number)
' DayOfYear, Weekday, Day:
dateValue.AddDays(number)
' WeekOfYear:
dateValue.AddDays(number * 7)
' Hour:
dateValue.AddHours(number)
' Minute:
dateValue.AddMinutes(number)
' Second:
dateValue.AddSeconds(number)

' Current day:
Dim todayStart As DateTime = DateTime.Today
Dim todayEnd As DateTime = todayStart.AddDays(1).AddSeconds(-1)

' Current month:
Dim monthStart As New DateTime(DateTime.Today.Year, DateTime.Today.Month, 1)
Dim monthEnd As DateTime = monthStart.AddMonths(1).AddSeconds(-1)

' Current year:
Dim yearStart As New DateTime(DateTime.Today.Year, 1, 1)
Dim yearEnd As DateTime = yearStart.AddYears(1).AddSeconds(-1)

Me.DataGridViewX1.DataSource = dsSSNregioni

Me.DataGridViewX1.DataSource = dsSSNregioni.Tables(0)