CODEWITHSUNDEEP
vb.net
Quattro
Quattro

Reputation: 19

Variable X has been used before it's been declared

I'm not sure why I'm getting a warning from Visual Studio for the code below:

Dim cmd As SqlCommand
cmd.Parameters.AddWithValue("@password", pw.tostring)
 Try
            myconn.open
            cmd = New SqlCommand("UPDATE Customers SET PW2=@password WHERE ID=@id", myconn)

This is the warning message I get: Severity Code Description Project File Line Suppression State Warning BC42104 Variable 'Cmd' is used before it has been assigned a value. A null reference exception could result at runtime.
Appreciate any help

Upvotes: 0

Views: 95

Answers (1)

Scott Marcus
Scott Marcus

Reputation: 65806

You are accessing the Parameters property of cmd:

 Dim cmd As SqlCommand
 cmd.Parameters.AddWithValue("@password", pw.tostring) ' <== You can't use cmd yet!

before you instantiate it in the try:

  Try
        myconn.open

        ' This is where you are instantiating the object instance:
        cmd = New SqlCommand("UPDATE Customers SET PW2=@password WHERE ID=@id", myconn)

If you change to this, it will work:

 Dim cmd As SqlCommand
 cmd = New SqlCommand("UPDATE Customers SET PW2=@password WHERE ID=@id", myconn)

 ' You could combine the two above lines into one like this:
 'Dim cmd As New SqlCommand("UPDATE Customers SET PW2=@password WHERE ID=@id", myconn)

 cmd.Parameters.AddWithValue("@password", pw.tostring)

  Try
        myconn.open

This is also better, because only the myconn.open instruction should be in the Try/Catch since it is the only line that can cause an exception. Try/Catch should only be used around code that can cause an exception through no fault of the developer's. Adding a parameter to a command won't do that, but actual database interaction can.

Upvotes: 3

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