• 0

how to check if datareader is null or not [VB]


Question

hey

how to check if DataReader is null or not in VB.net??

this is my code

   
Function GetBrandID(ByVal BrandName As String) As Integer
	    Dim rdr1 As MySqlDataReader
	    Dim cmd1 As MySqlCommand
	    cmd1 = New MySqlCommand("select BrandID from Brand where Des like'" & BrandName & "%'", conTmp)
	    rdr1 = cmd1.ExecuteReader
	    rdr1.Read()
	    If Not rdr1 Is Nothing Then			  'this doesn't work
		    Dim ID As Integer = rdr1(0)
		    rdr1.Close()
		    Return ID
	    Else
	    End If
  End Function

plz help

7 answers to this question

Recommended Posts

  • 0

Function GetBrandID(ByVal BrandName As String) As Integer
Dim rdr1 As MySqlDataReader
Dim ID As Integer = -1
Dim cmd1 As MySqlCommand
cmd1 = New MySqlCommand("select BrandID from Brand where Des like'" & BrandName & "%'", conTmp) 'I should slap myself for using a LIKE on a query where I only want one row, I should SHOOT myself for not using a procedure...
rdr1 = cmd1.ExecuteReader
If rdr1.HasRows Then
rdr1.Read()
ID = rdr1.Item(0).value.ToInt32
End If

Return ID 'Now returns a value on all code paths; -1 would indicate an error
End Function
[/CODE]

  • 0
  On 26/01/2012 at 18:22, paxa said:

why not try this:

if (rdr1.hasrows)

or try this:

rdr.read()

any of them should do the trick, so just adjust your code accordingly

didnt knew read() is a function and it returns a Boolean value (must read MSDN documentation :ermm: ) . it works like a charm .thnx :punk:

  • 0

If you are only returning one value in your query, you can use ExecuteScalar instead of using a data reader. Also, you should use a parameterized query. If your "BrandName" variable has a quote in it the query will cause an unhandled exception. You can code something like this:



Dim objTemp As Object
Dim cmd As New SqlCommand

With cmd
.Connection = conTmp
.CommandText = "SELECT BrandID FROM Brand WHERE Des LIKE @parm1"
.Parameters.Add("@parm1lDbType.NVarChar).Value = BrandName & "%"
objTemp = .ExecuteScalar
End With

If IsDBNull(objTemp) OrElse objTemp Is Nothing OrElse IsNumeric(objTemp) = False Then
Return -1
Else
Return objTemp
End If

[/CODE]

  • Like 1
  • 0
  On 27/01/2012 at 20:34, apple jacks48 said:

If you are only returning one value in your query, you can use ExecuteScalar instead of using a data reader. Also, you should use a parameterized query. If your "BrandName" variable has a quote in it the query will cause an unhandled exception. You can code something like this:



Dim objTemp As Object
Dim cmd As New SqlCommand

With cmd
.Connection = conTmp
.CommandText = "SELECT BrandID FROM Brand WHERE Des LIKE @parm1"
.Parameters.Add("@parm1lDbType.NVarChar).Value = BrandName & "%"
objTemp = .ExecuteScalar
End With

If IsDBNull(objTemp) OrElse objTemp Is Nothing OrElse IsNumeric(objTemp) = False Then
Return -1
Else
Return objTemp
End If

[/CODE]

didnt knew that. thnx

This topic is now closed to further replies.
  • Posts

    • Go ###### yourself Apple. What an embarassing piece of ###### company.
    • From code to combat: Meta CTO calls for Silicon Valley involvement in military contracts by Hamid Ganji This week, Meta announced a partnership with the defense technology startup Anduril to build next-gen VR/AR extended reality headsets for the US military. Microsoft was given the contract in 2018, and the headsets were supposed to be built based on Microsoft HoloLens. Earlier this year, Microsoft gave up the entire project to Anduril but kept its role as the cloud services provider. Meta's Chief Technology Officer (CTO) is now calling for more Silicon Valley involvement in military contracts. Speaking at the Bloomberg Tech summit in San Francisco (via: Business Insider), Andrew Bosworth said the recent partnership between Meta, Anduril, and the US military could be a "return to grace" for Silicon Valley. "The Valley was founded on a three-way investment between the military, academics, and private industry. That was the founding of it," Bosworth said. Meta's CTO added that building VR/AR headsets for the US military doesn't turn the company into a defense contractor. He also said it was "way too early" to determine whether military contracts would become a business segment for Meta. "So far, it's like a zero. Let's start with one and go from there. I think there's no reason it couldn't be meaningful in the impact that it has," he added. The US military's desire for AI-powered tools and weapons has turned Big Tech into military contractors, whether willingly or unwillingly. Companies like Microsoft, Google, and Meta have a long history of providing services to the military and law enforcement agencies. The relationship between tech firms and the defense segment has always been controversial. In the most recent case, a group of Microsoft employees protested against the company's partnership with the Israeli military, which led to the layoff of the protesting staff.
    • Or run msinfo32! With Windows 11, Microsoft believes it has reinvented the wheel?
    • The long-awaited Nothing Phone (3) is finally coming next month, launch date confirmed by Aditya Tiwari London-based consumer electronics brand Nothing is due to launch its latest flagship in 2025. The company dropped a new teaser for the Phone (3), revealing when the flagship device will be out on the market. Nothing Phone (3) will be unveiled during a live event on July 1 at 1:00 PM ET / 10:00 AM PT / 6:00 PM BST / 11:30 PM IST. It has already created a live event titled "Come to Play" on its official YouTube channel, for which you can add a reminder by clicking on the "Notify Me" button. Nothing CEO Carl Pei has previously dropped several details about the unreleased smartphone. He took part in a social media AMA earlier this year and said Nothing Phone (3) will arrive in the third quarter of 2025. Pei confirmed that Nothing Phone (3) will make its way to the US this time after a dry spell since 2023. However, he didn't specify whether the device will be sold directly or through the beta channel, which currently includes Phone (3a), Phone (3a) Pro, and CMF Phone 2 Pro. The US has been a rocky terrain for Nothing. Its first smartphone was made available through the beta channel, and the Nothing Phone (2) is the only smartphone from the company that has been widely available in the US. The Glyph interface featured on the back of Nothing smartphones has remained a differentiating factor from the start. However, the smartphone maker recently posted a 9-second video in which the Glyph lights on the back of a Nothing smartphone abruptly turn off. "We killed the Glyph Interface," the company said. It makes sense when you check out the Phone (3) teaser and see dot matrix-style lights being flashed in a pattern. Nothing released another teaser about a week ago, featuring the number 3 lit up as dot matrix LEDs. If you're looking for some trivia, Nothing product manager Raymond Zhu estimated in a Q&A video that the company would need to sell about 250,000 Phone (3) units to turn a profit. Answering another question, he added that their biggest weakness is "no one knows us", and the company is struggling to reach the masses without high marketing budgets. Let's wait to see what Nothing has in store for Phone (3) next month other than the new physical button. Speaking of the future of smartphones, the Nothing CEO believes that our entire software experience will eventually be condensed down to just one app.
    • As far as I can remember, no one has done a 4v4 before. 2v2? yes. 3v3? yes.
  • Recent Achievements

    • Week One Done
      jbatch earned a badge
      Week One Done
    • First Post
      Yianis earned a badge
      First Post
    • Rookie
      GTRoberts went up a rank
      Rookie
    • First Post
      James courage Tabla earned a badge
      First Post
    • Reacting Well
      James courage Tabla earned a badge
      Reacting Well
  • Popular Contributors

    1. 1
      +primortal
      403
    2. 2
      +FloatingFatMan
      179
    3. 3
      snowy owl
      174
    4. 4
      ATLien_0
      170
    5. 5
      Xenon
      135
  • Tell a friend

    Love Neowin? Tell a friend!