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

[Shane Ekanayake]

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

[paxa]

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

[jakem1]

Do While rdr1.read
	ID = rdr1(0)
Loop

If ID = 0 Then ...[/CODE]

You might want to ensure that your select query only returns a single row.

[Kami-]

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]

[Shane Ekanayake]

  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:

[paxa]

you're welcome

[apple jacks48]

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]

[Shane Ekanayake]

  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