Pull value from SQL Server in VB.NET - sql-server

Question

I am attempting to pull values from an SQL Server table from VB.NET.
On VB Form 1, the number from NoTable, Row 1, is pulled successfully, and Label1 is updated with the value.
Dim command As SqlCommand
Dim query As String = "SELECT Number FROM NoTable"
command = New SqlCommand(query, con)
con.Open()
Dim datareader As SqlDataReader = cmd.ExecuteReader()
If datareader.Read() Then
Label1.Text = datareader.GetValue(0)
End If
datareader.Close()
On VB Form 2 I am attempting to pull the value from the second row, using:
Dim query As String = "SELECT Number FROM NoTable"
command = New SqlCommand(query, con)
con.Open()
Dim datareader As SqlDataReader = cmd.ExecuteReader()
If datareader.Read() Then
Label1.Text = datareader.GetValue(1)
End If
datareader.Close()
However, this does not work, and the label is not updated with the value from the second row.
An unhandled exception of type 'System.IndexOutOfRangeException' occurred in System.Data.dll
Additional information: Index was outside the bounds of the array."
How would I go about fixing this, so that on Form 2, the value from Row 2 is pulled, and so forth?
Thank you.

Answer 1

Firstly, you only get one column back from the reader, but you are indexing the columns with that 0 or 1. So you should always pass 0 to GetValue.
To index the row instead, try this. Assign a form number to each form (first line in my example) and use that to determine which record to assign to the Label. There is probably a more efficient way to do this (not returning all the records before it) but this solution should fit in your environment.
' in form # 1
Dim formNumber = 1
Dim command As SqlCommand
Dim query As String = "SELECT Number FROM NoTable"
command = New SqlCommand(query, con)
con.Open()
Dim datareader As SqlDataReader = cmd.ExecuteReader()
Dim index = 0
While index < formNumber
If datareader.Read() AndAlso index = formNumber Then
Label1.Text = datareader.GetValue(0)
End If
index += 1
End While
datareader.Close()
See https://msdn.microsoft.com/en-us/library/system.data.sqlclient.sqldatareader.getvalue(v=vs.110).aspx
And another similar question in c# Access a specific row in DataReader
Another way is to just return the row you need in the first place, without iterating over the records on the client side. Assuming there is another column with an index which is in the same order as the row you want to return, called "ID"
' in form # 1
Dim formNumber = 1
Dim command As SqlCommand
Dim query As String =
"SELECT Number FROM " & _
" (SELECT Number, Row_Number() OVER (ORDER BY ID) AS RowNumber " & _
" FROM NoTable) AS Results " & _
" WHERE Results.RowNumber = " & formNumber.ToString()
command = New SqlCommand(query, con)
con.Open()
Dim datareader As SqlDataReader = cmd.ExecuteReader()
Label1.Text = datareader.GetValue(0)
datareader.Close()
See https://msdn.microsoft.com/en-us/library/ms186734.aspx

Answer 2

GetValue(1) does not exist, as this would refer to a second column in the select statement. You are only asking for [Number] which would be datareader.GetValue(0)