How to change the background color of a certain row in a DataGrid

Question

For example, in xaml I have a DataGrid named PersonList:

<DataGrid Name="PersonList" />

In the codebehind I have a collection of Person:

ObservableCollection<Person> persons = ViewModel.PersonModel;

And then I created a Person DataTable, and binded it to the PersonList in the following way:

PersonDataTable.Columns.Add("Name", typeof(string));
PersonDataTable.Columns.Add("Age", typeof(int));

foreach (var person in persons)
{
    if (person != null)
    {
        PersonDataTable.Rows.Add(
            Person.Name,
            Person.Age
            );
    }
}
PersonList.ItemSource = PersonDataTable.AsDataView;

My Question is, how to change the background color of a certain row? For example, change the background color of the row with the person's age > 50

I tried to do it by accessing each row from the PersonList.ItemSource, but I failed and the row is always null:

int count = 0;
foreach (var person in PersonList.ItemSource)
{
    var row = PersonList.ItemContainerGenerator.ContainerFromItem(person) as DataGridRow;
    if (PersonDataTable.Rows[count].Field<int>(1) > 50)
    {
        row.Background = Brushes.Gray;
    }
    count++;
}

Please help, WPF masters :)

Answer 1

Try your logic using converter as shown below:

Here is my AgeAboveLimitConverter file :

using System;
using System.Windows.Data;

namespace DataGridSample.Converter
{
    public class AgeAboveLimitConverter : IValueConverter
    {
        public object Convert(object value, Type targetType, object parameter, System.Globalization.CultureInfo culture)
        {
            if (value != null)
            {
                return (int)value > 50;
            }

            return false;
        }

        public object ConvertBack(object value, Type targetType, object parameter, System.Globalization.CultureInfo culture)
        {
            return null;
        }
    }
}

And then in your datagrid xaml file, add namespace xmlns:converter="clr-namespace:DataGridSample.Converter"

Add Style for DataGridRow in DataGrid,

<Grid>
        <Grid.Resources>
            <converter:AgeAboveLimitConverter x:Key="AgeConverter"/>
        </Grid.Resources>
        <DataGrid Name="PersonList">
            <DataGrid.RowStyle>
                <Style TargetType="DataGridRow" >
                    <Setter Property="Background"  Value="Transparent" />
                    <Style.Triggers>
                        <DataTrigger Binding="{Binding Path=Age,Converter={StaticResource AgeConverter}}" Value="true">
                            <Setter Property="Background" Value="Red"/>
                        </DataTrigger>
                    </Style.Triggers>
                </Style>
            </DataGrid.RowStyle>
        </DataGrid>
    </Grid>

Answer 2

You were almost there. Try the following:

int count = 0;
foreach (var person in PersonList.ItemSource)
{
    var row = PersonList.ItemContainerGenerator.ContainerFromItem(person) as DataGridRow;
    if (PersonDataTable.Rows[count].Field<int>(1) > 50)
    {
        row.DefaultCellStyle.BackColor = Color.Gray; 
    }
    count++;
}