OracleLob.Write(Byte[], Int32, Int32) 方法

public:
 override void Write(cli::array <System::Byte> ^ buffer, int offset, int count);

public override void Write(byte[] buffer, int offset, int count);

override this.Write : byte[] * int * int -> unit

Public Overrides Sub Write (buffer As Byte(), offset As Integer, count As Integer)

参数

例外

注解

如果写入操作成功，流中的位置会按写入的字节数向前推进。 如果发生异常，则流中的位置保持不变。

允许超出末尾 LOB 的写入，并放大 LOB 写入的字节数。

Oracle 的 .NET Framework Data Provider 将所有 CLOB 和 NCLOB 数据作为 Unicode 进行处理。 因此，访问 CLOB 和 NCLOB 数据类型时，始终处理字节数，其中每个字符为 2 个字节。 例如，如果包含三个字符的文本字符串保存在 NCLOB 每个字符为 4 个字节的 Oracle 服务器上，并且执行 Write 操作，则指定字符串的长度为 6 个字节，尽管它在服务器上存储为 12 个字节。

若要写入， LOB必须在 SQL SELECT 语句中使用 FOR UPDATE 子句检索 LOB ，并且必须启动本地事务。

以下示例演示如何写入 OracleLob 对象：

public static void WriteLobExample(OracleCommand command)
{
    // Note: Updating LOB data requires a transaction.
    command.Transaction = command.Connection.BeginTransaction();
    // Select some data.
    //    Table Schema:
    //        "CREATE TABLE tablewithlobs (a int, b BLOB, c BLOB)";
    //        "INSERT INTO tablewithlobs values (1, 'AA', 'AAA')";
    command.CommandText = "SELECT * FROM TableWithLobs FOR UPDATE";
    OracleDataReader reader = command.ExecuteReader();
    using(reader)
    {
        // Obtain the first row of data.
        reader.Read();
        // Obtain both LOBs.
        OracleLob BLOB1 = reader.GetOracleLob(1);
        OracleLob BLOB2 = reader.GetOracleLob(2);
        // Perform any desired operations on the LOB, (read, position, and so on).
        // ...
        // Example - Writing binary data (directly to the backend).
        // To write, you can use any of the stream classes, or write raw binary data using
        // the OracleLob write method. Writing character vs. binary is the same;
        // however note that character is always in terms of Unicode byte counts
        // (for example: even number of bytes - 2 bytes for every Unicode character).
        var buffer = new byte[100];
        buffer[0] = 0xCC;
        buffer[1] = 0xDD;
        BLOB1.Write(buffer, 0, 2);
        BLOB1.Position = 0;
        Console.WriteLine(BLOB1.LobType + ".Write(" + buffer + ", 0, 2) => " + BLOB1.Value);

        // Example - Copying data into another LOB.
        long actual = BLOB1.CopyTo(BLOB2);
        Console.WriteLine(BLOB1.LobType + ".CopyTo(" + BLOB2.Value + ") => " + actual);

        // Commit the transaction now that everything succeeded.
        // Note: On error, Transaction.Dispose is called (from the using statement)
        // and will automatically roll-back the pending transaction.
        command.Transaction.Commit();
    }
}