Select a column from table with parameterized query

Question

1.00/5 (1 vote)

See more:

VB

ConnectData()
        DisableBtn(Me)
        DisableTxt(Me)
        EnableBtn(Me)
        CmbStyle(Me)
        BtnSave.Enabled = False
        CmbFind.Hide()
        Try
            Sqlcommand.CommandText = "Select Name from State_Mast"
            Sqlcommand.ExecuteNonQuery()
            Dim Da As New MySqlDataAdapter
            Da.SelectCommand = Sqlcommand()
            Da.Fill(Ds, "state")
            DBState.DataSource = Ds.Tables("state")
            DBState.ValueMember = "Name"
            DBState.DisplayMember = "Name"
            Da.Dispose()
        Catch ex As MySql.Data.MySqlClient.MySqlException
            MessageBox.Show(ex.Message)
        End Try

the Sqlcommand.CommandText = "Select Name from State_Mast" is throwing system.nullreferenceexcepton

What I have tried:

with the code below it worked fine

VB

Try
        ConnectData()
        DisableBtn(Me)
        DisableTxt(Me)
        EnableBtn(Me)
        CmbStyle(Me)
        BtnSave.Enabled = False
        CmbFind.Hide()
        Try
            SqlQuery = "Select Name from State_Mast"
            Sqlcommand = New MySqlCommand(SqlQuery, Conn)
            Dim count As String = Sqlcommand.ExecuteScalar
            Dim Da As New MySqlDataAdapter

            Da.SelectCommand = Sqlcommand
            Da.Fill(Ds, "state")
            DBState.DataSource = Ds.Tables("state")
            DBState.ValueMember = "Name"
            DBState.DisplayMember = "Name"
            Da.Dispose()

Catch ex As MySql.Data.MySqlClient.MySqlException
            MessageBox.Show(ex.Message)
        End Try

Posted 21-Oct-19 6:00am

Member 13550326

Updated 21-Oct-19 9:47am

Andy Lanng

v2

Add a Solution

Comments

Richard MacCutchan 21-Oct-19 12:01pm

You forgot to add a connection object.

Member 13550326 21-Oct-19 12:39pm

ConnectData() defines the connection.

Member 13550326 21-Oct-19 12:39pm

connectdata() defines connection

1 solution

Add a Solution

Add your solution here

Treat my content as plain text, not as HTML

Preview 0

…

Existing Members

Sign in to your account

...or Join us

Download, Vote, Comment, Publish.

Your Email
Password
Forgot your password?

Your Email
This email is in use. Do you need your password?
Optional Password

I have read and agree to the Terms of Service and Privacy Policy
Please subscribe me to the CodeProject newsletters

When answering a question please:

Read the question carefully.
Understand that English isn't everyone's first language so be lenient of bad spelling and grammar.
If a question is poorly phrased then either ask for clarification, ignore it, or edit the question and fix the problem. Insults are not welcome.
Don't tell someone to read the manual. Chances are they have and don't get it. Provide an answer or move on to the next question.

Let's work to help developers, not make them feel stupid.

This content, along with any associated source code and files, is licensed under The Code Project Open License (CPOL)

ZurdoDev · Answer 1 · 2019-10-21T09:47:00

Solution 1

Quote:
system.nullreferenceexcepton

This means something is null. In this case SelectCommand is null.

Quote:
Sqlcommand.CommandText = "Select Name from State_Mast"

You try to access the CommandText property of something that is null.

Posted 21-Oct-19 9:47am

ZurdoDev

Comments

Member 13550326 21-Oct-19 17:32pm

I didn't understand. Please tell what is the problem and show the right code for it.

ZurdoDev 21-Oct-19 19:50pm

SelectCommand is null. You have not initialized it.

Member 13550326 22-Oct-19 6:12am

I'm new to programming , tell me how should i initialise it.

ZurdoDev 22-Oct-19 6:38am

You said you have some code that works fine up above. So look at that and see where it gets initialized. Also go through examples online to learn how to use ADO.Net.