<DataGrid x:Name="employeeGrid" HorizontalAlignment="Center" VerticalAlignment="Center" AlternatingRowBackground="LightBlue" AlternationCount="2" AutoGenerateColumns="False" ItemsSource="{Binding}">
        <DataGrid.Columns>
            <DataGridTextColumn Header="Emp #" Binding="{Binding EmpId}"/>
            <DataGridTextColumn Header="First Name" Binding="{Binding FirstName}"/>
            <DataGridTextColumn Header="Last Name" Binding="{Binding LastName}"/>
        </DataGrid.Columns>
    </DataGrid>

Following goes in your corresponding .cs file:

employeeGrid.ItemsSource = employeeDetails;

<DataGrid x:Name="employeeGrid" HorizontalAlignment="Center" VerticalAlignment="Center" AlternatingRowBackground="LightBlue" AlternationCount="2" AutoGenerateColumns="False" ItemsSource="{Binding}">
    <DataGrid.Columns>
        <DataGridTextColumn Header="Emp #" Binding="{Binding EmpId}"/>
        <DataGridTextColumn Header="First Name" Binding="{Binding FirstName}"/>
        <DataGridTextColumn Header="Last Name" Binding="{Binding LastName}"/>
    </DataGrid.Columns>
</DataGrid>

Following goes in your corresponding .cs file:

employeeGrid.ItemsSource = employeeDetails;