fetching single value form database in vb.net - vb.net

Question

this my database table
id name
1   abc
2    xyz
it i enter 1 then respective value "abc" display in different text box???
Private Sub butsea_Click(sender As Object, e As EventArgs) Handles butsea.Click
Dim dset As New DataSet
Dim da As SqlDataAdapter
Dim myCmd As New SqlCommand
Try
myConn.ConnectionString = "Data Source=THEONE\PARTH;Initial Catalog=testdatabase;Integrated Security=True;"
myConn.Open()
Dim avalue As String = (InputBox("Input Student Id", "Search Student")).ToString
txt_id.Text = avalue
da = New SqlDataAdapter("SELECT * FROM studentdetails where student_id= '" & txt_id.Text & "", myConn)
If dset.Tables(0).Rows.Count > 0 Then
'what should i write here
Else
MsgBox("No Record Found")
End If
Catch ex As Exception
MsgBox(ex.Message)
Finally
myConn.Close()
End Try
End Sub

Answer 1

If you need to fetch just a single value - using DataAdapter and DataSet is overkill. Use SqlCommand.ExecuteScalar method and in your query instead of "SELECT * ..." do a "SELECT YOURFIELD ... ".
this way you don't have to jump thru hoops building a dataset, checking number of rows etc. and just check returned value for Nothing instead.
UPDATE Here is your code modified to use ExecuteScalar
Private Sub butsea_Click(sender As Object, e As EventArgs) Handles butsea.Click
Dim myCmd As SqlCommand
Dim myConn As New SqlConnection
Dim oResult As Object
Try
myConn.ConnectionString = "Data Source=THEONE\PARTH;Initial Catalog=testdatabase;Integrated Security=True;"
myConn.Open()
Dim avalue As String = (InputBox("Input Student Id", "Search Student")).ToString
txt_id.Text = avalue
myCmd = New SqlCommand("SELECT student_name FROM studentdetails where student_id= '" & txt_id.Text & "'", myConn)
oResult = myCmd.ExecuteScalar()
If oResult IsNot Nothing Then
txt_name.text = oResult.ToString
Else
MsgBox("No Record Found")
End If
Catch ex As Exception
MsgBox(ex.Message)
Finally
myConn.Close()
End Try
End Sub
This code assumes that database field that u need to display is called student_name and that you added TextBox called txt_name to your form.

Answer 2

You need to add other textboxes for every field you want to show.
(For example a textbox called txtStudentName could be used for the name, and so on for other fields present in the table studentdetails).
The correct way to query your database (leaving out other methods like using a SqlDataReader) should be the following
Dim dset As New DataSet
Dim da As SqlDataAdapter
Try
myConn.ConnectionString = "Data Source=THEONE\PARTH;Initial Catalog=testdatabase;Integrated Security=True;"
myConn.Open()
Dim avalue As String = (InputBox("Input Student Id", "Search Student")).ToString
txt_id.Text = avalue
' prepare the adapter with a commandtext. Do not use string concatenation from user input'
da = New SqlDataAdapter("SELECT * FROM studentdetails where student_id=#id", myConn)
da.SelectCommand.Parameters.AddWithValue("#id", txt_id.Text)
' Fill the dataset'
da.Fill(dset)
If dset.Tables(0).Rows.Count > 0 Then
' Supposing you have a field for the studentname in the first column of the returned
' datatable rows(rowindex)(columnindex)
txtStudentName.Txt = dset.Tables(0).Rows(0)(0).ToString()
.....
' Set the text property of other textboxes for other fields to show'
Else
MsgBox("No Record Found")
End If