Solved having to click twice to drop a DataGridViewComboBox

The default behaviour of a drop down combobox in a datagridview is for it to require one click to activate it and another to actually drop it down.

Users can’t get this paradigm and so prefer for it to activate immediately on clicking anywhere on the cell. I have seen many solutions on Stackoverflow for this, but most require the arrow part of the cell to be clicked, not working if the user just clicks the cell in the middle. 

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I found the following solution to work for me:

Private Sub DataGridView1_CellClick(sender As Object, e As DataGridViewCellEventArgs) _
Handles DataGridView1.CellClick
If (e.ColumnIndex > 0) And e.RowIndex <> -1 Then
With DirectCast(sender, DataGridView)
If .Columns(e.ColumnIndex).Name = "PalletType" Then
.CurrentCell = .Rows(e.RowIndex).Cells(e.ColumnIndex)
.BeginEdit(True)
DirectCast(.EditingControl, _
System.Windows.Forms.DataGridViewComboBoxEditingControl).DroppedDown = True
End If
End With
End If
End Sub

This makes certain the column is not a header cell, and only does it for the column with the name “PalletType”

I also have the DatagridView set to EditOnEnter for the Edit mode.

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WCF Service on Server 2012

The page you are requesting cannot be served because of the extension 
configuration. If the page is a script, add a handler. If the file should be 
downloaded, add a MIME map.

My first experiences with Server 2012 had me puzzled for a few mins when trying to get some WCF service end points transferred from another older 2003 server.

It was solved by going into server manager, drilling down in the add roles and features to the server concerned, selecting Features. under the .NET Framework 4.5 features there was WCF Services, after checking the box and under that also selecting HTTP Activation to on, everything sprang to life.

There are also 3.5 versions of these too if the application is running on the older framework.

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Progress messages from SQL Server to VB.NET/C# application

When executing long running queries on SQL server, the messages from PRINT statements do not return to the caller sometimes until the whole process is finished, or intermittently at best.

If running a long running process from the GUI or debugging in SQL server management studio, it can be desirable to let the user know where things are at and prevent them force quitting your application prematurely.

By using the following statement messages can be sent back immediately, note the NOWAIT, this forces the message back right away:

RAISERROR (N'working', 10,1) WITH NOWAIT

In the above example, 10 is the severity level of the error we are raising  and 1 the state. This is not severe enough to stop the statement running.

I use this all the time now for getting a feeling of security from seeing something happening on long running scripts.

ADO.NET

With C#/VB.NET using ADO.NET to connect to the procedure, we have a “infoMessage” event that is raised whenever a message comes back from SQL. By handling this event we can proceed to update the user GUI with that message, or another message as required.

cn.InfoMessage += delegate(object sender, SqlInfoMessageEventArgs e)
{
txtMessages.Text += "\n" + e.Message;
};

 

References:

Regarding hashing passwords .NET & Rfc2898DeriveBytes

I live outside the world of oAuth and need to hash passwords for authentication

For goodness sake don’t be tempted to write your own hash! Research the latest advise as it changes as machines and cracking advances. Swathes of passwords have been stolen from compromised sites in the past, and have been cracked and sold or given away. Don’t let your site be the source of misery!

Use well known hashing algorithm

Use the .NET class Rfc2898DeriveBytes that implements PBKDF2 for password hashing. This uses iterations to make it computationally expensive for any brute force attacks.

Use salt

To prevent attackers reverse engineering your users’ passwords using rainbow tables, and other colourful techniques, use the above class with a random salt per user hash. You need to store the salt in your data store, its ok to store it concatenated with password hash.

Use good random salt with high amount of entropy

Use a decent random generator such as that provided by the RNGCryptoServiceProvider  in the System.Security.Cryptography namespace to generate your salt, there are degrees of randomness, remember random is pseudo random in the random class in .NET.

Load the CPU with iterations

Choose a good number of iterations when generating the hash. To future proof your implementation, also store the number of iterations used to generate the hash against each user, with the hash and salt, in the data store. This makes it possible to “turn up” the number of iterations as machines get faster in the future and not “spoil” the existing hashes (obviously the hashes would be upgraded after login in this scenario).

Risks of Denial of Service (Dos)

Denial of Service, be aware that for this protection you are on purpose introducing a computationally expensive routine to the authentication methods of the site. This exposes a possible denial of service attack by bombarding the login method with authentication requests, some sort self healing technique to limit such an attack is required. Perhaps if high traffic is detected, temporarily add a capture to the login page to limit the DoS impact.