DataSource Controls :: Error Message: Incorrect Syntax Near ','

Can someone please tell me what normally causes this error message (stack trace at bottom of this post)? I can't even tell what line or what page is producing the error.

Following are the relevant (I think) 2 code procedures...the Update command below seems to "work", because later I see that the image is updated---but I can't immediately see that: I get the above error message.

'FormView.ItemUpdating Event
Protected Sub AdvertisementForm_ItemUpdating(ByVal sender As Object, ByVal e As System.Web.UI.WebControls.FormViewUpdateEventArgs) Handles AdvertisementForm.ItemUpdating
' Get the connection string from Web.config.
Using conn As New SqlConnection(ConfigurationManager.ConnectionStrings("MyDatabaseConnectionString").ToString())
' Create a command object.
Dim cmd As New SqlCommand()
' Assign the connection to the command.
cmd.Connection = conn
' Set the command text
' SQL statement or the name of the stored procedure.
cmd.CommandText = "UPDATE Advertisements SET UserName = @UserName, Age = @Age, Avatar = ISNULL(@Avatar, Avatar) WHERE UserId = @UserId"
' Set the command type
' CommandType.Text for ordinary SQL statements;
cmd.CommandType = CommandType.Text
' Get the person ID, first name and last name from the
' EditItemTemplate of the FormView control.
Dim strUserId As String = DirectCast(AdvertisementForm.Row.FindControl("UserIdTextBox"), TextBox).Text
Dim strUserName As String = DirectCast(AdvertisementForm.Row.FindControl("UserNameTextBox"), TextBox).Text
Dim strAge As String = DirectCast(AdvertisementForm.Row.FindControl("AgeTextBox"), TextBox).Text
' Append the parameters to the SqlCommand and set values.
cmd.Parameters.Add("@UserId", SqlDbType.UniqueIdentifier).Value = Guid.Parse(strUserId)
cmd.Parameters.Add("@UserName", SqlDbType.NChar).Value = strUserName
cmd.Parameters.Add("@Age", SqlDbType.NChar).Value = strAge
' Find the FileUpload control in the EditItemTemplate of
' the FormView control.
Dim uploadAvatar As FileUpload = DirectCast(AdvertisementForm.FindControl("uploadAvatar"), FileUpload)
If uploadAvatar.HasFile Then
' Append the Picture parameter to the SqlCommand.
' If a picture is specified, set the parameter with
' the value of bytes in the specified picture file.
cmd.Parameters.Add("@Avatar", SqlDbType.VarBinary).Value = uploadAvatar.FileBytes
Else
' Append the Picture parameter to the SqlCommand.
' If no picture is specified, set the parameter's
' value to NULL.
cmd.Parameters.Add("@Avatar", SqlDbType.VarBinary).Value = DBNull.Value
End If
' Open the connection.
conn.Open()
' Execute the command.
cmd.ExecuteNonQuery()
End Using
' Switch FormView control to the ReadOnly display mode.
AdvertisementForm.ChangeMode(FormViewMode.ReadOnly)
' Rebind the FormView control to show data after updating.
BindFormView()
End Sub
Private Sub BindFormView()
' Get the connection string from Web.config.
Using conn As New SqlConnection(ConfigurationManager.ConnectionStrings("MyDatabaseConnectionString").ToString())
' Create a DataSet object.
Dim dsPerson As New DataSet().
' Create a SELECT query.
Dim strSelectCmd As String = "SELECT UserId, Avatar FROM Advertisements"
' Create a SqlDataAdapter object
Dim da As New SqlDataAdapter(strSelectCmd, conn)
' Open the connection
conn.Open()
' Fill the DataTable named "Advertisements" in DataSet with the rows
' returned by the query.
da.Fill(dsAdvertisements, "Advertisements")
Dim dsAdvertisements As DataSet = New DataSet()
' Bind the FormView control.
AdvertisementForm.DataBind()
End Using
End Sub
Server Error in '/www.mywebsite.com' Application.
Incorrect syntax near ','.
[Code]....
Stack Trace: [Code]....