Working with DataGrid in VC++.NET

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Introduction

This is my small contribution from what I learnt in my walk towards VC++ .NET. It's a really simple and very often used scenario: working with DataGrid. Here, I developed a small application which creates database and stores the data (image), and also retrieves data from the database and displays it in the DataGrid.

Code Explanation

Requirements

• MS Visual Studio .NET 2003
• Windows XP
• SQL Server 2000

I used SQL Server for database operations. The application shows how the values (image) are stored in the database and the grid is updated when changes are made in the database. This is the snapshot of my application.

Controls used

• Buttons: Create Database, Select Image, Save to Database
• PictureBox: PictureBox1
• DataGrid: Datagrid1

Create the database

When you click the button 'Create Database', the table called Picture would be created in the SQL Server NorthWind database. If it is already present, it would be deleted and created again.

String* strSQL = 
        S"IF EXISTS (SELECT * FROM northwind.dbo.sysobjects WHERE NAME " 
        "= 'Picture' AND TYPE = 'u')\r\nBEGIN\r\nDROP " 
        "TABLE northwind.dbo.picture\r\nEND\r\nCREATE TABLE " 
        "Picture (PictureID Int IDENTITY(1,1) NOT NULL,[FileName] " 
        "Varchar(255) NOT NULL,Picture Image NOT NULL," 
        "CONSTRAINT [PK_Picture] PRIMARY KEY CLUSTERED(PictureID))";
Try
{
    SqlConnection* conCreate = new SqlConnection(strconString);
    SqlCommand* sqlCmd = new SqlCommand(strSQL,conCreate);
    conCreate->Open();
    sqlCmd->ExecuteNonQuery();
    conCreate->Close();

      MessageBox::Show(S"Table is Created Successfully",S"Table   
        Creation",MessageBoxButtons::OK,MessageBoxIcon::Information);

}
catch(System::Exception* ee)
{
    MessageBox::Show(ee->Message,S"Error",MessageBoxButtons::OK,
                         MessageBoxIcon::Information);
}

Place the code to create the table and declare the appropriate variables in the program.

Select Image

The open file dialog is used to select the particular image. When the Select Image button is clicked, the open file dialog would be displayed to select the image (BMP/GIF/JPG).

openFileDialog1->InitialDirectory = S"C:\\";
openFileDialog1->Filter = S"All
                    Files|*.*|Bitmaps|*.bmp|GIFs|*.gif|JPEGs|*.jpg";
openFileDialog1->FilterIndex = 2;

if(openFileDialog1->ShowDialog()== DialogResult::OK)
 {
 pictureBox1->Image = Image::FromFile(openFileDialog1->FileName);
 pictureBox1->SizeMode = PictureBoxSizeMode::CenterImage;
 pictureBox1->BorderStyle = BorderStyle::Fixed3D;
 lblImage_Path->Text = openFileDialog1->FileName;

 }

Place the code in the Select Image button Click event.

Save to Database

When the Save to Database button is clicked, the selected image would be stored into the Picture table by means of converting it into a stream of bytes. After storing into database, refresh the DataGrid.

//To Convert the Image to Bytes
MemoryStream* mst = new MemoryStream();
pictureBox1->Image->Save(mst,pictureBox1->Image->RawFormat);
Byte BinaryImg[] = mst->GetBuffer();
mst->Close();

Then, insert the image name to the database.

//Insert into Table
conNwnd = new SqlConnection(strconString);
String* strSQL = S"INSERT INTO Picture" 
                  " (Filename, Picture)VALUES (@Filename, @Picture)";

//To Fill the DataGrid

sqlcmd = new SqlCommand(strSQL,conNwnd);
sqlcmd->Parameters->Add(new SqlParameter(S"@Filename", 
        SqlDbType::NVarChar,50))->Value = strImgFile[0];
sqlcmd->Parameters->Add(new SqlParameter(S"@Picture", 
        SqlDbType::Image))->Value = BinaryImg;

conNwnd->Open();
sqlcmd->ExecuteNonQuery();
conNwnd->Close();
RefreshTable();
MessageBox::Show(String::Concat(strImgFile[0],S" saved to Database."), 
       S"Image Status",MessageBoxButtons::OK,MessageBoxIcon::Information);

Here, RefreshTable function is used to refresh the grid.

RefreshTable()
conNwnd = new SqlConnection(strconString);
SqlDataAdapter* sqlDA = new SqlDataAdapter(S"Select PictureID,Filename," 
                        "Picture FROM Picture",conNwnd);
TableData->Clear();
sqlDA->Fill(TableData,INPUT_TABLE);
dataGrid1->DataSource = TableData->Tables->Item[INPUT_TABLE];

On the form Load call, this RefreshTable function displays the values from the database.

Conclusion

Using this small application, a beginner can understand the DataGrid and about database connections, and how to store and retrieve values from the database using VC++ .NET. Your comments are always welcome which helps me to sharp my knowledge more.