Retrieve data from database in asp.net using vb - vb.net

Question

Below is the code for fetching the data into textbox but its not working it shows error no data exits row/column whereas data and datafield are perfectly alright.
Please help.
Dim Connection As OleDbConnection
Connection = New OleDbConnection("Provider=Microsoft.Jet.OLEDB.4.0;Data Source=" & Server.MapPath("/db/QardanHasana.mdb"))
Connection.Open()
Dim ejamaatregcmd As OleDbCommand
Dim ejamaatregdtrdr As OleDbDataReader
ejamaatregcmd = New OleDbCommand("SELECT ITSData.[EJamaatID], ITSData.[ITSFirstName] FROM ITSData WHERE EjamaatID= #EjamaatID", Connection)
ejamaatregcmd.Parameters.Add(New OleDbParameter("#EjamaatID", txtEjamaatID.Text))
ejamaatregdtrdr = ejamaatregcmd.ExecuteReader()
If ejamaatregdtrdr.HasRows Then
txtFirstName.Text = ejamaatregdtrdr.item("ITSFirstName").ToString()
end if

Answer 1

A DataReader needs a call to Read to position itself on the first record retrieved
ejamaatregdtrdr = ejamaatregcmd.ExecuteReader()
If ejamaatregdtrdr.HasRows Then
ejamaatregdtrdr.Read()
txtFirstName.Text = ejamaatregdtrdr.item("ITSFirstName").ToString()
End if
By the way, Read returns false if there are no rows to read, so you could remove the test for HasRows and write simply
ejamaatregdtrdr = ejamaatregcmd.ExecuteReader()
If ejamaatregdtrdr.Read() Then
txtFirstName.Text = ejamaatregdtrdr.item("ITSFirstName").ToString()
End if
Another suggestion to improve your code is to start using the Using Statement
Using Connection = New OleDbConnection("Provider=Microsoft.Jet.OLEDB.4.0;....")
Using ejamaatregcmd = new OleDbCommand("SELECT ITSData.[EJamaatID], ITSData.[ITSFirstName] FROM ITSData WHERE EjamaatID= #EjamaatID", Connection)
Connection.Open()
ejamaatregcmd.Parameters.Add(New OleDbParameter("#EjamaatID", txtEjamaatID.Text))
Using ejamaatregdtrdr = ejamaatregcmd.ExecuteReader()
If ejamaatregdtrdr.Read() Then
txtFirstName.Text = ejamaatregdtrdr.item("ITSFirstName").ToString()
End if
End Using
End Using
End Using
The using statement is invaluable to help you to close and dispose the disposable objects like the connection, the command and the reader. Lacking a proper dispose your code uses more memory and locks resources resulting in a more unstable application.

Answer 2

Before reading data from a DataReader, you need to move the row to the first row by calling the Read method. It returns true if data exist, so you don't need to check the HasRows property:
ejamaatregdtrdr = ejamaatregcmd.ExecuteReader()
If ejamaatregdtrdr.Read() Then
txtFirstName.Text = ejamaatregdtrdr.Item("ITSFirstName").ToString()
End if

Answer 3

I'll generally do something like the following
Function GetResult(ID As string) As String
GetResult = "No Data" 'Default Result
Dim conn As System.Data.OleDb.OleDbConnection = *NewConnectionObject*
Dim comm As System.Data.OleDb.OleDbCommand = *NewCommmandObject*
comm.Parameter.AddWithValue("#Parametername",ID)
Using reader As System.Data.OleDb.OleDbDataReader = comm.ExecuteReader()
If reader.HasRows Then
'Reader has data, so iterate through it
GetResult = ""
while reader.read
GetResult += reader("FirstName")
End While
Else
'Either Do Nothing - Default Result will show
'Throw New System.Exception("Empty Data") 'Try Catch Statement have overhead.. so it's not a popular methodology
'Or Log Something..
End If
End Using
If conn.state = connection.open Then
conn.close
End
End Function