Load data into DataGridView from sql server in vb - sql

Question

Loading data from SQL server into datagridview but Warning 1 Variable 'dtApplicantLists' is used before it has been assigned a value. A null reference exception could result in runtime. green underline at dtApplicantLists.Load(reader)
Any help, please...
Private Function GetList() As DataTable
Dim dtApplicantLists As DataTable
Dim connString As String = ConfigurationManager.ConnectionStrings("dbx").ConnectionString
Using conn As New SqlConnection(connString)
Using cmmd As New SqlCommand("SELECT FirstName, LastName, Gender, ChosenProg, Aggregate FROM dbo.Applicants", conn)
conn.Open()
Dim reader As SqlDataReader = cmmd.ExecuteReader()
dtApplicantLists.Load(reader)
End Using
End Using
Return dtApplicantLists
End Function

Answer 1

You need to call dtApplicantLists = New DataTable - currently it is null (or Nothing in VB).

Answer 2

Using ... End Using Method will guarantee you won't need to worry about warnings like this one you got, as obviously demonstrated in your Code.
Private Function GetList() As DataTable
Dim SqlStr As String =
("SELECT FirstName, LastName, Gender, ChosenProg, Aggregate FROM dbo.Applicants")
Using dtApplicantLists As DataTable = New DataTable
Using conn As New SqlConnection(ConfigurationManager.ConnectionStrings("dbx").ConnectionString),
Cmd As New SqlCommand(SqlStr, conn)
conn.Open()
Using Reader As SqlDataReader = Cmd.ExecuteReader
dtApplicantLists.Load(Reader)
End Using
End Using
Return dtApplicantLists
End Using
End Function

Answer 3

You can do it this way.
Imports System.Data.SqlClient
Public Class Form1
Dim connetionString As String
Dim connection As SqlConnection
Dim adapter As SqlDataAdapter
Dim cmdBuilder As SqlCommandBuilder
Dim ds As New DataSet
Dim changes As DataSet
Dim sql As String
Dim i As Int32
Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
connetionString = "Data Source=ServerName;Initial Catalog=DatabaseName;User ID=UserName;Password=Password"
connection = New SqlConnection(connetionString)
Sql = "select * from Product"
Try
connection.Open()
adapter = New SqlDataAdapter(Sql, connection)
adapter.Fill(ds)
connection.Close()
DataGridView1.Data Source= ds.Tables(0)
Catch ex As Exception
MsgBox(ex.ToString)
End Try
End Sub
Private Sub Button2_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button2.Click
Try
cmdBuilder = New SqlCommandBuilder(adapter)
changes = ds.GetChanges()
If changes IsNot Nothing Then
adapter.Update(changes)
End If
MsgBox("Changes Done")
Catch ex As Exception
MsgBox(ex.ToString)
End Try
End Sub
End Class
See the link below for some other similar, but slightly different options.
http://vb.net-informations.com/dataadapter/dataadapter-datagridview-sqlserver.htm