Question

VS.C#如何向数据数据库中存入和读取图片的?

Answer 1

首先，在数据库中要建立相应的字段能保存Bytes，例如在SQL Server中用Image类型来定义字段。我所用到的数据库大致结构如下：

字段名
类型
备注

FileID
Int
自增字段

FileName
Varchar(256)

FullName
Varchar(1024)

FileData
Image

然后就是写入数据库，代码如下：

FileInfo fi = new FileInfo( txtFileName.Text );// Replace with your file name

if ( fi.Exists)

{

byte[] bData = null;

int nNewFileID = 0;

// Read file data into buffer

using ( FileStream fs = fi.OpenRead() )

{

bData = new byte[fi.Length];

int nReadLength = fs.Read( bData,0, (int)(fi.Length) );

}

// Add file info into DB

string strQuery = "INSERT INTO FileInfo "

+ " ( FileName, FullName, FileData ) "

+ " VALUES "

+ " ( @FileName, @FullName, @FileData ) "

+ " SELECT @@IDENTITY AS 'Identity'";

SqlCommand sqlComm = new SqlCommand( strQuery, sqlConn );

sqlComm.Parameters.Add( "@FileName", fi.Name );

sqlComm.Parameters.Add( "@FullName", fi.FullName );

sqlComm.Parameters.Add( "@FileData", bData );

// Get new file ID

SqlDataReader sqlReader = sqlComm.ExecuteReader();

if( sqlReader.Read() )

{

nNewFileID = int.Parse(sqlReader.GetValue(0).ToString());

}

sqlReader.Close();

sqlComm.Dispose();

if( nNewFileID > 0 )

{

// Add new item in list view

ListViewItem itmNew = lsvFileInfo.Items.Add( fi.Name );

itmNew.Tag = nNewFileID;

}

}

而读出的代码如下：

// Get new file name

string strFullName = dlgFBSave.SelectedPath;

if( strFullName[strFullName.Length - 1] != '\\' )

strFullName += @"\";

strFullName += lsvFileInfo.SelectedItems[0].Text;

string strQuery = "SELECT FileData FROM FileInfo "

+ " WHERE FileID = " + lsvFileInfo.SelectedItems[0].Tag.ToString();

SqlDataAdapter sqlDAdapter = new SqlDataAdapter(strQuery,sqlConn);

DataSet sqlRecordSet = new DataSet();

byte[] bData = null;

//Get file data from DB

try

{

sqlDAdapter.Fill( sqlRecordSet, "FileInfo" );

foreach( DataRow dr in sqlRecordSet.Tables["FileInfo"].Rows)

{

if( dr["FileData"] != DBNull.Value )

bData = ( byte[] )dr["FileData"];

}

}

catch(SqlException sqlErr)

{

MessageBox.Show( sqlErr.Message );

}

catch

{

MessageBox.Show( "Failed to read data from DB!" );

}

sqlRecordSet.Dispose();

sqlDAdapter.Dispose();

if( bData != null )

{

// Save file

FileInfo fi = new FileInfo( strFullName );

if( !fi.Exists )

{

//Create the file.

using (FileStream fs = fi.Create())

{

fs.Write( bData, 0, bData.Length);

}

}

else

{

//Create the file.

using (FileStream fs = fi.OpenWrite())

{

fs.Write( bData, 0, bData.Length);

}

}

}

不过需要提的一点，如果把大量的文件存入数据库的话，会造成数据库的臃肿，而且访问量也会增大。所以现在比较流行的做法，是把文件上传到服务器上，而在数据库上只保存文件的相对路径即可。那么访问的时候，先通过数据库得到文件的相对路径，然后再访问服务器上的文件

Answer 2

写入图片部分代码：
假设图片为 test.gif
byte [] bytes = File.ReadAllBytes(@"c:\test.gif");
SqlConnection con = new SqlConnection("server=.;uid=sa;pwd=xxx;database=数据库名");
con.open();
SqlCommand cmd = new SqlCommand("insert into 表(图片字段) values(@image)");
cmd.Parameters.Add("@image", SqlDbType.Image).Value = bytes;
cmd.ExecuteNonQuery();
读取部分代码：
SqlConnection con = new SqlConnection("server=.;uid=sa;pwd=xxx;database=数据库名");
con.open();
SqlCommand cmd = new SqlCommand("select 图片字段 表 where 图片编号=1");
object scalar = scmd.ExecuteScalar();
byte[] bytes=(byte[])scalar;

如果保存成文件：
File.WriteAllBytes(@"c:\read.gif",bytes);
如果要直接用网页输出：
MemoryStream ms = new MemoryStream(bytes);
Response.ContentType = "image/gif";
System.Drawing.Image image=System.Drawing.Image.FromStream(ms);
image.Save(Response.OutputStream, System.Drawing.Imaging.ImageFormat.Gif);
Response.End();