Can not figure out why datagridview isn't updating with new information after a SQL statement using a string builder

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VB

SQL

here is my code:

Dim sqlconn As New SqlConnection("sqlconnectionstring")
            Dim da As New SqlDataAdapter(String.Empty, sqlconn)

            Dim sql As New StringBuilder("insert into [")
            sql.Append(Form1.TreeView1.SelectedNode.Text.Replace("]", "\]"))
            sql.Append("] ([Id], ")

            Dim sbOn As New StringBuilder(") values(@Id, ")
            Dim andRequired As Boolean = False

            If Not String.IsNullOrEmpty(IDTextBox.Text) Then
                da.SelectCommand.Parameters.AddWithValue("@Id", 
            Form1.DataGridView1.Rows.Count + 1)
            End If

            If Not String.IsNullOrEmpty(First_NameTextBox.Text) Then
                If andRequired Then
                    sql.Append(", ")
                    sbOn.Append(", ")
                End If

                sql.Append("[First_name]")
                sbOn.Append("@Firstname")

                da.SelectCommand.Parameters.AddWithValue("@Firstname", First_NameTextBox.Text)
                andRequired = True
            End If
sql.AppendFormat(sbOn.ToString + ")")
            da.SelectCommand.CommandText = sql.ToString()
            Dim dt As New DataTable
            da.Fill(dt)
            DataGridView1.DataSource = dt

when this is used the sql string comes out right, but the datagridview that its connected to turns gray and shows no data, but if I restart the program it will show the new data.

What I have tried:

tried to change the da.selectcommand to a da.insertcommand. Also tried to change things around a use a new sql command to correspond to the Dataadaptor, but that didn't work either.