Urgente Error

[mjesus20]

TENGO EL SIGUIENTE ERROR

No se ha inicializado la propiedad SelectCommand antes de llamar a 'Fill'.

Y TENGO EL SIGUIENTE CODIGO DONDE SE ME PRODUCE ESE ERROR ALGUIEN ME PODRIA DECIR QUE ME FALTA


Dim connectionString As String = "server='192.168.100.254'; user id='SA'; password=''; database='Sistema Administrativo'; trusted_connection=true"
Dim queryString As String = "SELECT[Inventario].[Item], [Inventario].[Modelo], [Inventario].[Inventario], [Inventario].[Equipo], [Inventario].[Fecha Compra], [Inventario].[Serie], [Inventario].[Valor Compra], [Inventario].[Lugar], [Inventario].[Ubicacion] FROM [Inventario]"
Dim isediting As Boolean = False


Private Sub page_load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
If Not Page.IsPostBack Then
bindgrid()
End If
End Sub


Sub bindgrid()
Dim dbConnection As System.Data.IDbConnection = New System.Data.SqlClient.SqlConnection(connectionStri ng)
Dim dbCommand As System.Data.IDbCommand = New System.Data.SqlClient.SqlCommand()
Dim dataadapter As System.Data.IDbDataAdapter = New System.Data.SqlClient.SqlDataAdapter()
Dim dataset As System.Data.DataSet = New System.Data.DataSet()
dataadapter.Fill(dataset)
DataGrid1.DataSource = dataset
DataGrid1.DataBind()
End Sub