本文给出一个用 C# 编程实现读写 Binary 的实例代码
以下是引用片段：
//返回blob数据
public MemoryStream getBlob(string SQL)
...{
try
...{
Db_Conn();
cmd = new OleDbCommand(SQL, Conn);
cmd.CommandType = CommandType.Text;//是sql
OleDbDataReader Rs = cmd.ExecuteReader();
if (Rs.Read()) //循环到下一条记录
...{
if (!(Rs.GetValue(0) is System.DBNull))
...{
byte[] image_bytes = (byte[])Rs.GetValue(0);
MemoryStream ms = new MemoryStream(image_bytes);
return ms;
}
else
return null;
}
else
return null;
}
finally
...{
this.close();
}
}
//设置blob
public bool SetBlob(string SQL, MemoryStream Ms)
...{
try
...{
Db_Conn();
cmd = new OleDbCommand(SQL, Conn);
cmd.CommandType = CommandType.Text;//是sql
int n=Convert.ToInt32(Ms.Length.ToString());
Ms.Position = 0;
byte[] pReadByte = new Byte[n];
Ms.Read(pReadByte, 0, n);
cmd.Parameters.Add("BLOB", OleDbType.Binary).Value = pReadByte;
cmd.ExecuteNonQuery();
return true;
}
catch (Exception ex)
...{
MessageBox.Show("错误:因" + ex.Message + ",无法执行:" + SQL);
return false;
}
finally
...{
this.close();
}
}
调用 getBlob
以下是引用片段：
String sqlStr = "select content from dp where id=" + ID;//content为dp中的BLOB字段,ID为主键
MemoryStream ms = DBClass.getBlob(sqlStr);
if (ms == null)
richTextBox.Clear();
else
...{
if (ms.Length > 0)
...{
ms.Position = 0;
try
...{
richTextBox.LoadFile(ms, RichTextBoxStreamType.RichText);
}catch...{
richTextBox.LoadFile(ms, RichTextBoxStreamType.PlainText);
}
}else
richTextBox.Clear();
}
调用setBlob
以下是引用片段：
String sqlStr = "update dp set content=:BLOB where id=" + ID;
MemoryStream ms = new MemoryStream();
richTextBox.SaveFile(ms, RichTextBoxStreamType.RichText);
if (!DBClass.SetBlob(sqlStr, ms))
...{
MessageBox.Show("保存失败");
}
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