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，则流中的位置将按写入的字节数前进。 如果发生异常，则流中的位置保持不变。

允许在 末尾 LOB 之外写入 ，并按写入的字节数放大 LOB 。

用于 Oracle 的 .NET Framework 数据提供程序以 Unicode 的形式处理所有数据CLOBNCLOB。 因此，在访问 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在 Oracle 服务器上保存为 ， NCLOB 该字符串的字符集为每个字符 4 个字节，并且您执行操作 Write 时，可以将字符串的长度指定为 6 个字节，尽管该字符串在服务器上存储为 12 个字节。

若要写入 到 ， 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();  
    }  
}  

适用于