Two row display the same in datagrid after refresh datagrid

I have a project, entering different data on 2 rows(or more than 2 rows) of datagrid (using C #, WPF, database: sql server), after refreshing the datagrid, result:data 2-rows display similar (similar to the last row input)
   data 2-rows display in the database is different (this is expected on the datagrid).
What happened?

Description:
   Input data in two row:
     row 1: MachineId = 1, MachineName = A;
     row 2: MachineId = 2, MachineName = B;
   After refresh datagrid:
     row 1: MachineId = 2, MachineName = B;
     row 2: MachineId = 2, MachineName = B;
   How are do display data the same...:
     row 1: MachineId = 1, MachineName = A;
     row 2: MachineId = 2, MachineName = B;

public partial class Machine : INotifyPropertyChanged
    {
        public int MachineId { get; set; }
        public string MachineName { get; set; }
       
        public event PropertyChangedEventHandler PropertyChanged;
    }

<DataGrid x:Name="dgMachine" ItemsSource="{Binding MachineList}">            
           <DataGrid.Columns>
                <DataGridTextColumn x:Name="dgtMachineId"  
                    Binding="{Binding MachineId}"
                    Header="MachineId"/>
                <DataGridTextColumn x:Name="dgtMachineName"  
                    Binding="{Binding MachineName}"
                    Header="MachineName" />
            </DataGrid.Columns>
</DataGrid>

dgMachine.ItemsSource = null;
dgMachine.ItemsSource = ViewModel.MachineList;

I think the problem in the datagrid, but do not know what is