VB-SQL, Exception in SELECT statement - mysql

Question

Imports System.Data.SqlClient
Public Class Form3
Private cs As New SqlConnection("Data Source=HUSAIN-PC;Initial
Catalog=final1;Integrated Security=True")
Private da As New SqlDataAdapter
Private ds As New DataSet
Public dr As SqlDataReader
Public cmd As New SqlCommand
Private sql As String
Private sqlsel As String
Dim Bal As String
Dim id As String
Dim amt As String
Private Sub Form3_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
End Sub
Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
cs.Open()
cmd.Connection = cs
amt = TextBox2.Text
id = TextBox1.Text
sqlsel = "SELECT (Bal) FROM db5 WHERE Id='" + id + "'"
da.InsertCommand = New SqlCommand(sqlsel, cs)
dr = cmd.ExecuteReader
If dr.HasRows = True Then
While (dr.Read())
Bal = dr("Id")
End While
End If
dr.Close()
MessageBox.Show("Balance is :" + Bal)
Dim total As String = Bal + amt
sql = "UPDATE db5 SET Bal='" + total + "' WHERE Id='" + id + "'"
da.InsertCommand = New SqlCommand(sql, cs)
da.InsertCommand.ExecuteNonQuery()
MessageBox.Show("updated")
End Sub
End Class
This is my VB code to retrieve a value from the SQL DB...the Update statement is running fine bt wen i write the select i get an exception in the code:
dr=cmd.ExecuteReader
"ExecuteReader: CommandText property has not been initialized"

Answer 1

Look at this code:
sqlsel = "SELECT (Bal) FROM db5 WHERE Id='" + id + "'"
da.InsertCommand = New SqlCommand(sqlsel, cs)
dr = cmd.ExecuteReader
You're specifying an InsertCommand as a SELECT query, but then you're calling ExecuteReader on a completely separate SqlDataReader... which hasn't got a query configured, as per the error message.
That's why you're getting this specific error, but there are lots of problems with this code:
You should be creating a new SqlConnection / SqlCommand etc every time you want to execute a query
You should be using Using statements to automatically close them
You shouldn't have instance variables for these - they should be local variables
I see no reason to use a DataAdapter here in the first place - just use SqlCommand.ExecuteNonQuery
Very important: You should be using parameterized SQL instead of including values directly in your SQL. See the Bobby Tables site for more information about this topic.