這里有關(guān)于用C#讀取數(shù)據(jù)庫(kù)中的Image數(shù)據(jù)的介紹，
誰(shuí)知道該怎么把image對(duì)象寫入數(shù)據(jù)庫(kù)，？以及對(duì)數(shù)據(jù)庫(kù)中image對(duì)象
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從數(shù)據(jù)庫(kù)中獲取 BLOB 值

DataReader 的默認(rèn)行為是在整個(gè)數(shù)據(jù)行可用時(shí)立即以行的形式加載傳入數(shù)據(jù)。但是，對(duì)于二進(jìn)制大對(duì)象 (BLOB) 則需要進(jìn)行不同的處理，因?yàn)樗鼈兛赡馨�含�?shù)十億字節(jié)的數(shù)據(jù)，而單個(gè)行中無(wú)法包含如此多的數(shù)據(jù)。Command.ExecuteReader 方法具有一個(gè)重載，它將采用 CommandBehavior 參數(shù)來(lái)修改 DataReader 的默認(rèn)行為。您可以將 CommandBehavior.SequentialAccess 傳遞到 ExecuteReader 方法來(lái)修改 DataReader 的默認(rèn)行為，以便讓 DataReader 按照順序在接收到數(shù)據(jù)時(shí)立即將其加載，而不是加載數(shù)據(jù)行。這是加載 BLOB 或其他大數(shù)據(jù)結(jié)構(gòu)的理想方案。

在將 DataReader 設(shè)置為使用 SequentialAccess 時(shí)，務(wù)必要注意訪問(wèn)所返回字段的順序。DataReader 的默認(rèn)行為是在整個(gè)行可用時(shí)立即加載該行，這使您能夠在讀取下一行之前按任何順序訪問(wèn)所返回的字段。但是，當(dāng)使用 SequentialAccess 時(shí)，必須按順序訪問(wèn)由 DataReader 返回的不同字段。例如，如果查詢返回三個(gè)列，其中第三列是 BLOB，則必須在訪問(wèn)第三個(gè)字段中的 BLOB 數(shù)據(jù)之前返回第一個(gè)和第二個(gè)字段的值。如果在訪問(wèn)第一個(gè)或第二個(gè)字段之前訪問(wèn)第三個(gè)字段，則第一個(gè)和第二個(gè)字段值將不再可用。這是因?yàn)?SequentialAccess 已修改 DataReader，使其按順序返回?cái)?shù)據(jù)，當(dāng) DataReader 已經(jīng)讀取超過(guò)特定數(shù)據(jù)時(shí)，該數(shù)據(jù)將不可用。

當(dāng)訪問(wèn) BLOB 字段中的數(shù)據(jù)時(shí)，請(qǐng)使用 DataReader 的 GetBytes 類型化訪問(wèn)器，該訪問(wèn)器將使用二進(jìn)制數(shù)據(jù)填充 byte 數(shù)組。您可以指定要返回的特定數(shù)據(jù)緩沖區(qū)大小以及從返回的數(shù)據(jù)中讀取的第一個(gè)字節(jié)的起始位置。GetBytes 將返回 long 值，它表示所返回的字節(jié)數(shù)。如果向 GetBytes 傳遞空的 byte 數(shù)組，所返回的長(zhǎng)值將是 BLOB 中字節(jié)的總數(shù)。您可以選擇將字節(jié)數(shù)組中的某索引指定為所讀取數(shù)據(jù)的起始位置。

以下示例從 Microsoft SQL Server 中的 pubs 示例數(shù)據(jù)庫(kù)中返回發(fā)行者 ID 和徽標(biāo)。發(fā)行者 ID (pub_id) 是字符字段，而徽標(biāo)則是圖形，即 BLOB。請(qǐng)注意，由于必須按順序訪問(wèn)字段，所以將在訪問(wèn)徽標(biāo)之前訪問(wèn)當(dāng)前數(shù)據(jù)行的發(fā)行者 ID。

[Visual Basic]
Dim pubsConn As SqlConnection = New SqlConnection("Data Source=localhost;Integrated Security=SSPI;Initial Catalog=pubs;")
Dim logoCMD As SqlCommand = New SqlCommand("SELECT pub_id, logo FROM pub_info", pubsConn)

Dim fs As FileStream ' Writes the BLOB to a file (*.bmp).
Dim bw As BinaryWriter ' Streams the binary data to the FileStream object.

Dim bufferSize As Integer = 100' The size of the BLOB buffer.
Dim outbyte(bufferSize - 1) As Byte' The BLOB byte() buffer to be filled by GetBytes.
Dim retval As Long ' The bytes returned from GetBytes.
Dim startIndex As Long = 0 ' The starting position in the BLOB output.

Dim pub_id As String = ""' The publisher id to use in the file name.

' Open the connection and read data into the DataReader.
pubsConn.Open()
Dim myReader As SqlDataReader = logoCMD.ExecuteReader(CommandBehavior.SequentialAccess)

Do While myReader.Read()
' Get the publisher id, which must occur before getting the logo.
pub_id = myReader.GetString(0)

' Create a file to hold the output.
fs = New FileStream("logo" & pub_id & ".bmp", FileMode.OpenOrCreate, FileAccess.Write)
bw = New BinaryWriter(fs)

' Reset the starting byte for a new BLOB.
startIndex = 0

' Read bytes into outbyte() and retain the number of bytes returned.
retval = myReader.GetBytes(1, startIndex, outbyte, 0, bufferSize)

' Continue reading and writing while there are bytes beyond the size of the buffer.
Do While retval = bufferSize
bw.Write(outbyte)
bw.Flush()

' Reposition the start index to the end of the last buffer and fill the buffer.
startIndex = startIndex + bufferSize
retval = myReader.GetBytes(1, startIndex, outbyte, 0, bufferSize)
Loop

' Write the remaining buffer.
bw.Write(outbyte)
bw.Flush()

' Close the output file.
bw.Close()
fs.Close()
Loop

' Close the reader and the connection.
myReader.Close()
pubsConn.Close()
[C#]
SqlConnection pubsConn = new SqlConnection("Data Source=localhost;Integrated Security=SSPI;Initial Catalog=pubs;");
SqlCommand logoCMD = new SqlCommand("SELECT pub_id, logo FROM pub_info", pubsConn);

FileStream fs;// Writes the BLOB to a file (*.bmp).
BinaryWriter bw;// Streams the BLOB to the FileStream object.

int bufferSize = 100; // Size of the BLOB buffer.
byte[] outbyte = new byte[bufferSize];// The BLOB byte[] buffer to be filled by GetBytes.
long retval;// The bytes returned from GetBytes.
long startIndex = 0;// The starting position in the BLOB output.

string pub_id = ""; // The publisher id to use in the file name.

// Open the connection and read data into the DataReader.
pubsConn.Open();
SqlDataReader myReader = logoCMD.ExecuteReader(CommandBehavior.SequentialAccess);

while (myReader.Read())
{
// Get the publisher id, which must occur before getting the logo.
pub_id = myReader.GetString(0);

// Create a file to hold the output.
fs = new FileStream("logo" + pub_id + ".bmp", FileMode.OpenOrCreate, FileAccess.Write);
bw = new BinaryWriter(fs);

// Reset the starting byte for the new BLOB.
startIndex = 0;

// Read the bytes into outbyte[] and retain the number of bytes returned.
retval = myReader.GetBytes(1, startIndex, outbyte, 0, bufferSize);

// Continue reading and writing while there are bytes beyond the size of the buffer.
while (retval == bufferSize)
{
bw.Write(outbyte);
bw.Flush();

// Reposition the start index to the end of the last buffer and fill the buffer.
startIndex+= bufferSize;
retval = myReader.GetBytes(1, startIndex, outbyte, 0, bufferSize);
}

// Write the remaining buffer.
bw.Write(outbyte);
bw.Flush();

// Close the output file.
bw.Close();
fs.Close();
}

// Close the reader and the connection.
myReader.Close();
pubsConn.Close();