学步园

public bool ReadFlashCard(int x)
 {
   try
   {

// dispose of the old image and  set the picture box to null
     if (pictureBox1.Image != null)
         pictureBox1.Image.Dispose();

         pictureBox1.Image = null;

// form a query that will only select the flashcard we are interested in

          sqlDataAdapter1.SelectCommand.CommandText = "Select * From Flashcards Where PrimaryKey = "
             +            Convert.ToString(x);

//  Fill the dataset using the query from the adapter

         DataSet ds = new DataSet();

        sqlDataAdapter1.Fill(ds, "Flashcards");

//  Hide the labels that contain the answer to the flashcard

        label1.Visible = false;
        label2.Visible = false;

// if no row is returned it means we reached the end or something is wrong    

     if (ds.Tables[0].Rows.Count == 0)
          return false;

// populate the hidden answers:  the language word and the pronunciation

  label1.Text = ds.Tables[0].Rows[0]["LearnLanguage"].ToString();
  label2.Text = ds.Tables[0].Rows[0]["Pronunciation"].ToString();

//  now we need to get the picture from the DataRow
//  and assign it to a byte array

  byte[] MyData = null;
  MyData = (byte[])ds.Tables[0].Rows[0]["Picture"];

//  After retrieving the byte array, we want to get the 
//  number of elements of the array for use in writing the array

   int ArraySize = new int();
  ArraySize = MyData.GetUpperBound(0);

//  Create a Filestream for writing the byte array to a gif file (the original format in this case)
  FileStream fs = new FileStream("tmp.gif", FileMode.OpenOrCreate, FileAccess.Write);

//  Write the stream of data that we read in from the database to the filestream and close it.
//  This will create the file  tmp.gif, which we can use to display in the picturebox

  fs.Write(MyData, 0,ArraySize+1); // don't ask me why, but I had to add 1 here for this to work
  fs.Close();

//  Assign the temporary gif file to the picture box

  pictureBox1.Image = new Bitmap("tmp.gif");
  return true;

}
catch (Exception ex)
 {
  MessageBox.Show(ex.Message.ToString());
  return false;
  }

}

private void button2_Click(object sender, System.EventArgs e)
{
 try
  {

//  Fill a DataSet with existing Flashcards
    DataSet ds = new DataSet();
   sqlDataAdapter1.Fill(ds, "Flashcards");
   DataTable TheTable = ds.Tables[0];

// Create a new row for the FlashCard Table in Memory 
   DataRow aRow = TheTable.NewRow();
  
//  Insert the information from the dialog into the Flashcard Table 
//  Such as the Primary Key, Language Word, Translation, and Pronunciation
   aRow["PrimaryKey"] = TheTable.Rows.Count + 1;
   aRow["LearnLanguage"] = textBox1.Text;
   aRow["FirstLanguage"] = textBox2.Text;
   aRow["Pronunciation"] = textBox3.Text;

//  Create a new FileStream for reading data from the image file  in which the PictureBox populated
//  Its data from (the FileName is maintained after the picture button is pressed and a picture is selected).

   FileStream fs = new FileStream (FileName, FileMode.OpenOrCreate,
                                                FileAccess.Read);

//   Read the Data into the Byte Array

    byte[] MyData = new byte[fs.Length];
   fs.Read(MyData, 0, (int)fs.Length);
   fs.Close();

//  Assign the DataRow Picture Column to the Byte Array to populate it in the DataRow

   aRow["Picture"] = MyData;

//   Add the DataRow to the DataTable

   TheTable.Rows.Add(aRow);

//  Write all  the data (including the picture) to the Flashcards Sql Server database

   sqlDataAdapter1.Update(ds, "Flashcards");

    MessageBox.Show("Flashcard Added.");

}

catch (Exception ex)

{
    MessageBox.Show(ex.Message.ToString());
}

}

Michael Gold is President of Microgold Software Inc., makers of the WithClass UML Tool. His company is a Microsoft VBA Partner and Borland Partner. He has a BSEE and MEng EE from Cornell University and has consulted for Chase Manhattan Bank, Merrill Lynch. Currently he is a senior consultant at JP Morgan Bank. He has been involved in several .NET book projects, and is currently working on a book for using .NET with embedded systems. He can be reached at techsupport@microgold.com