Avoid too much IF ELSE when filter 10 combobox VB.NET

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Hi,
I'm currently using IF ELSE method to filter data with lot of combobox.
What i did is something like this :

VB

IF cboName.text = "" AND cboAge.text = "" THEN
     select name,age from tbUser
ELSEIF cboName.text <> "" AND cboAge.text = "" THEN
     select name,age from tbUser WHERE name = '" & cboName.text & "'

ELSEIF cboName.text = "" AND cboAge.text <> "" THEN
     select name,age from tbUser WHERE age = '" & cboAge.text & "'
ELSEIF cboName.text <> "" AND cboAge.text <> "" THEN
     select name,age from tbUser WHERE name = '" & cboName.text & "' AND age = '" & cboAge.text & "'
END IF

And if i have 10 combobox, there will be hundreds of line just for doing this process.

Any suggestion to doing this process effectively?
Thank you.

What I have tried:

IF cboName.text = "" AND cboAge.text = "" THEN
     select name,age from tbUser
ELSEIF cboName.text <> "" AND cboAge.text = "" THEN
     select name,age from tbUser WHERE name = '" & cboName.text & "'

ELSEIF cboName.text = "" AND cboAge.text <> "" THEN
     select name,age from tbUser WHERE age = '" & cboAge.text & "'
ELSEIF cboName.text <> "" AND cboAge.text <> "" THEN
     select name,age from tbUser WHERE name = '" & cboName.text & "' AND age = '" & cboAge.text & "'

Posted 22-Nov-22 15:51pm

Copycat Studio

Updated 22-Nov-22 16:29pm

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Comments

Richard Deeming 23-Nov-22 4:28am

Your code is almost certainly vulnerable to SQL Injection[^]. NEVER use string concatenation/interpolation to build a SQL query. ALWAYS use a parameterized query.

Copycat Studio 25-Nov-22 4:03am

Thank you for your advice. I am using this app in small local network.

Richard Deeming 25-Nov-22 4:05am

So you implicitly trust every single person who has a device on that network, and are happy to teach them why they can't search for "O'Connor"?

And you're absolutely confident that no device on that network will ever be infected with malware or otherwise compromised by hackers?

Remember, when you're defending a system against potential threats, you have to be right every time. A hacker only has to be right once.

Copycat Studio 25-Nov-22 4:22am

Yes i get the point. And yes, it will result an Error when user type single quote char. I'm just newbie vb.net programmer and still lot things to learn. I made apps for my small team and they all just don't know how PC/program work. They only taught how to input. Anyway, again thanks for your advice.

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Graeme_Grant · Answer 1 · 2022-11-22T16:29:00

You are building a query, you will need to check every choice that is available to the user.

What you can do is build the query as you go.
The Select is always the same:

VB

Dim QueryString = new StringBuilder()
Dim WhereBuilder = new List(Of String)()

QueryString.Append("select name, age from tbUser")

Then do each test:

VB

If Not String.IsNullOrWhitespace(cboName.Text) Then
    WhereBuilder.Add("name = '" + cboName.Text + "'")
End If

If Not String.IsNullOrWhitespace(cboAge.Text) Then
    WhereBuilder.Add("age = '" + cboAge.Text + "'")
End If

Now you are ready to build the query:

VB

If WhereBuilder.Count > 0 Then
    QueryString.Append(" where ")
    QueryString.Append(String.Join(" and ", WhereBuilder)
End If

dim query = QueryString.ToString()

NOTE: Code is written in the answer untested, so may need cleaning up.