How do i handle a multiple null image values from Microsoft SQL Server database with vb.net code - vb.net

Question

I was hoping someone could point me in the right direction with my current code. I'm getting an error while opening my program:
Data is Null. This method or property cannot be called on null values.
I put an else statement for btn.backgroundimage but still get that error.
Here is what my code looks like:
Sub FillItems()
Try
con = New SqlConnection(cs)
con.Open()
Dim PictureCol As Integer = 1 ' the column # of the BLOB field
Dim cmdText1 As String = "SELECT RTRIM(ProductName),Image from Temp_Stock_Company INNER JOIN Product ON Product.PID=Temp_Stock_Company.ProductID where ShowPOS='Yes'"
cmd = New SqlCommand(cmdText1)
cmd.Connection = con
cmd.CommandTimeout = 0
rdr = cmd.ExecuteReader()
flpItems.Controls.Clear()
Do While (rdr.Read())
'Dim btn As New Button
'btn.Text = rdr.GetValue(0)
'btn.TextAlign = ContentAlignment.MiddleCenter
'btn.BackColor = Color.SteelBlue
'btn.ForeColor = Color.White
'btn.FlatStyle = FlatStyle.Popup
'btn.Width = 125
'btn.Height = 60
'btn.Font = New System.Drawing.Font("Microsoft Sans Serif", 10.0!, System.Drawing.FontStyle.Regular, System.Drawing.GraphicsUnit.Point, CType(0, Byte))
'UserButtons.Add(btn)
'flpItems.Controls.Add(btn)
Dim b(rdr.GetBytes(PictureCol, 0, Nothing, 0, Integer.MaxValue) - 1) As Byte
rdr.GetBytes(PictureCol, 0, b, 0, b.Length)
Dim ms As New System.IO.MemoryStream(b)
Dim Dflp As New FlowLayoutPanel
Dflp.Size = New System.Drawing.Size(197, 197)
Dflp.BackColor = Color.Black
Dflp.BorderStyle = BorderStyle.None
Dflp.FlowDirection = FlowDirection.TopDown
Dim btn As New Button
Dim btnX As New Button
btn.Text = rdr.GetValue(0)
btn.Width = 197
btn.Height = 197
If DBNull.Value.Equals(rdr(1)) = False Then
btn.BackgroundImage = Image.FromStream(ms)
btn.BackgroundImageLayout = ImageLayout.Stretch
Else
btn.BackgroundImage = My.Resources._12
btn.BackgroundImageLayout = ImageLayout.Stretch
End If
btn.FlatStyle = FlatStyle.Flat
btn.FlatAppearance.BorderSize = 0
btn.Text = rdr.GetValue(0)
btn.Font = New System.Drawing.Font("Segoe UI Semibold", 1.0!, System.Drawing.FontStyle.Bold, System.Drawing.GraphicsUnit.Point, CType(0, Byte))
btn.TextAlign = System.Drawing.ContentAlignment.BottomCenter
btn.ForeColor = System.Drawing.Color.Black
btnX.Text = rdr.GetValue(0)
btnX.FlatStyle = FlatStyle.Flat
btnX.Width = 0
btnX.Height = 0
btnX.FlatAppearance.BorderSize = 0
btnX.Text = rdr.GetValue(0)
btnX.Font = New System.Drawing.Font("Segoe UI Semibold", 8.0!, System.Drawing.FontStyle.Bold, System.Drawing.GraphicsUnit.Point, CType(0, Byte))
btnX.TextAlign = System.Drawing.ContentAlignment.MiddleCenter
btnX.ForeColor = Color.White
btnX.BackColor = Color.SteelBlue
UserButtons.Add(btn)
UserButtons.Add(btnX)
Dflp.Controls.Add(btn)
Dflp.Controls.Add(btnX)
flpItems.Controls.Add(Dflp)
AddHandler btn.Click, AddressOf Me.btnItems_Click
AddHandler btnX.Click, AddressOf Me.btnItems_Click
Loop
con.Close()
Catch ex As Exception
MessageBox.Show(ex.Message, "Error", MessageBoxButtons.OK, MessageBoxIcon.[Error])
End Try
End Sub

Answer 1

You do not want to hold the connection open while you update the user interface so I have used a DataTable which will hold your data after the connection is closed and disposed. Using...End Using blocks will close and dispose your database objects. Any class in the framework that shows you a .Dispose method should be enclosed in Using blocks. This includes streams.
Load the DataTable. Check for DBNull and only then get your byte array.
I used AdventureWorks (a sample database available from Microsoft) to test.
Private Sub Button2_Click(sender As Object, e As EventArgs) Handles Button2.Click
Dim dt As New DataTable
Using cn As New SqlConnection(My.Settings.Adventure),
cmd As New SqlCommand("Select Top 10 ProductPhotoID, ThumbNailPhoto From Production.ProductPhoto;", cn)
cn.Open()
Using reader = cmd.ExecuteReader
dt.Load(reader)
End Using
End Using
For Each row As DataRow In dt.Rows
Dim btn As New Button
If Not IsDBNull(row(1)) Then
Dim b() As Byte = DirectCast(row(1), Byte())
Using ms As New System.IO.MemoryStream(b)
btn.BackgroundImage = Image.FromStream(ms)
End Using
Else
btn.BackgroundImage = Image.FromFile("C:\Users\***\Desktop\Graphics\TreeFrog.jpg")
End If
btn.BackgroundImageLayout = ImageLayout.Stretch
btn.Width = 50
btn.Height = 50
FlowLayoutPanel1.Controls.Add(btn)
Next
End Sub