ExecuteReader: CommandText property has not been initialized when trying to make a register form for my database - vb.net

Question

hello guys im trying to script a register form for my database and i came with this code >> so can anyone help ?
Private Sub Button2_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button2.Click
Dim cn As New SqlConnection
Dim cmd As New SqlCommand
Dim dr As SqlDataReader
cn.ConnectionString = "Server=localhost;Database=test;Uid=sa;Pwd=fadyjoseph21"
cmd.Connection = cn
cmd.CommandText = "INSERT INTO test2(Username,Password) VALUES('" & TextBox1.Text & "','" & TextBox2.Text & "')"
cn.Open()
dr = cmd.ExecuteReader
If dr.HasRows Then
MsgBox("You're already registered")
Else
MsgBox("Already registered")
End If
End Sub

Answer 1

Edit your Code in this way..
cmd.CommandText = "INSERT INTO User_Data(Username,Password) VALUES('" & TextBox1.Text & "' , '" & TextBox2.Text & "')"
cn.Open()
cmd.ExecuteNonQuery()
cn.Close()
Insert will not retrieve any records it's a SELECT statement you want to use .I'll suggest you use stored procedures instead to avoid Sql-Injections.

Answer 2

ExecuteReader it's for "SELECT" queries, that helps to fill a DataTable. In this case you execute command before cmd.commandText is defined.
You should have define cmd.commandText before and use ExecuteNonQuery after, like this.
Dim cn As New SqlConnection
Dim cmd As New SqlCommand
cn.ConnectionString = "Server=localhost;Database=test;Uid=sa;Pwd=fadyjoseph21"
cmd.Connection = cn
cn.Open()
cmd.CommandText = "INSERT INTO User_Data(Username,Password) VALUES('" & TextBox1.Text & "','" & TextBox2.Text & "')"
cmd.ExecuteNonQuery()
cn.Close()

Answer 3

cmd.CommandText should be assigned stored proc name or actual raw SQL statement before calling cmd.ExecuteReader
Update:
Change code as follows
....
cmd.Connection = cn
cmd.CommandText = "select * from TblToRead where <filter>" ''This is select query statement missing from your code
cn.Open()
dr = cmd.ExecuteReader ....
where <filter> will be something like username = "' & Request.form("username') & '" '

Answer 4

The error itself is happening because you're trying to execute a query before you define that query:
dr = cmd.ExecuteReader
'...
cmd.CommandText = "INSERT INTO User_Data(Username,Password) VALUES('" & TextBox1.Text & "' and '" & TextBox2.Text & "')"
Naturally, that doesn't make sense. You have to tell the computer what code to execute before it can execute that code:
cmd.CommandText = "INSERT INTO User_Data(Username,Password) VALUES('" & TextBox1.Text & "' and '" & TextBox2.Text & "')"
'...
dr = cmd.ExecuteReader
However, that's not your only issue...
You're also trying to execute a DataReader, but your SQL command doesn't return data. It's an INSERT command, not a SELECT command. So you just need to execute it directly:
cmd.CommandText = "INSERT INTO User_Data(Username,Password) VALUES('" & TextBox1.Text & "' and '" & TextBox2.Text & "')"
cmd.ExecuteNonQuery
One value you can read from an INSERT command is the number of rows affected. Something like this:
cmd.CommandText = "INSERT INTO User_Data(Username,Password) VALUES('" & TextBox1.Text & "' and '" & TextBox2.Text & "')"
Dim affectedRows as Int32 = cmd.ExecuteNonQuery
At this point affectedRows will contain the number of rows which the query inserted successfully. So if it's 0 then something went wrong:
If affectedRows < 1 Then
'No rows were inserted, alert the user maybe?
End If
Additionally, and this is important, your code is wide open to SQL injection. Don't directly execute user input as code in your database. Instead, pass it as a parameter value to a pre-defined query. Basically, treat user input as values instead of as executable code. Something like this:
cmd.CommandText = "INSERT INTO User_Data(Username,Password) VALUES(#Username,#Password)"
cmd.Parameters.Add("#Username", SqlDbType.NVarChar, 50).Value = TextBox1.Text
cmd.Parameters.Add("#Password", SqlDbType.NVarChar, 50).Value = TextBox2.Text
(Note: I guessed on the column types and column sizes. Adjust as necessary for your table definition.)
Also, please don't store user passwords as plain text. That's grossly irresponsible to your users and risks exposing their private data (even private data on other sites you don't control, if they re-use passwords). User passwords should be obscured with a 1-way hash and should never be retrievable, not even by you as the system owner.

Answer 5

You're attempting to change the CommandText after you're executing your query.
Try this:
Private cn = New SqlConnection("Server=localhost;Database=test;UID=sa;PWD=secret")
Private Sub Button2_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button2.Click
Dim cmd As New SqlCommand
cmd.CommandText = "select * from table1" ' your sql query selecting data goes here
Dim dr As SqlDataReader
cmd.Connection = cn
cn.Open()
dr = cmd.ExecuteReader
If dr.HasRows = 0 Then
InsertNewData(TextBox1.Text, TextBox2.Text)
Else
MsgBox("Already registered")
End If
End Sub
Private Sub InsertNewData(ByVal username As String, ByVal password As String)
Dim sql = "INSERT INTO User_Data(Username,Password) VALUES(#Username, #Password)"
Dim args As New List(Of SqlParameter)
args.Add(New SqlParameter("#Username", username))
args.Add(New SqlParameter("#Password", password))
Dim cmd As New SqlCommand(sql, cn)
cmd.Parameters.AddRange(args.ToArray())
If Not cn.ConnectionState.Open Then
cn.Open()
End If
cmd.ExecuteNonQuery()
cn.Close()
End Sub
This code refers the INSERT command to another procedure where you can create a new SqlCommand to do it.
I've also updated your SQL query here to use SqlParameters which is much more secure than adding the values into the string directly. See SQL Injection.
The InsertNewData method builds the SQL Command with an array of SQLParameters, ensures that the connection is open and executes the insert command.
Hope this helps!