How to programmatically select the records of the Master-DetailsView at run time in WPF ?

int parentRowIndex =45, childRowIndex = 1;
private void btn_Click(object sender, RoutedEventArgs e)
{            
    //Checks whether the given index is parent row index or not. 
    bool IsDetailsViewIndex=this.dataGrid.IsInDetailsViewIndex(parentRowIndex);            
    if(IsDetailsViewIndex==true)
    {
        MessageBox.Show("Specified Index is  not valid parent row index ");
        return;
    }
    //Gets the record of the parent row index.
    var record = this.dataGrid.View.Records[this.dataGrid.ResolveToRecordIndex(parentRowIndex)];
    //Gets the DetailsViewManager by using Reflection.
    var propertyInfo = dataGrid.GetType().GetField("DetailsViewManager", System.Reflection.BindingFlags.Instance | System.Reflection.BindingFlags.NonPublic);
    DetailsViewManager detailsViewManager = propertyInfo.GetValue(dataGrid) as DetailsViewManager;
    // Checks whether the parent record has the child grid or not by getting the child source and its count.
    var childSource = detailsViewManager.GetChildSource(record.Data, "OrderDetails");
    var GetChildSourceCount = detailsViewManager.GetType().GetMethod("GetChildSourceCount", System.Reflection.BindingFlags.Instance | System.Reflection.BindingFlags.NonPublic | System.Reflection.BindingFlags.Static);
    var ChildSourceCount = GetChildSourceCount.Invoke(detailsViewManager,new object[]{childSource});                             
    if ((int)ChildSourceCount == 0)
    {
        MessageBox.Show("Child grid doesn't contains any record");
        return;
    }         
    //Checks whether the record is Expanded or Collapsed.
    //When it is in the collapsed state, you need to expand the particular DetailsView based on the index.
    if (!record.IsExpanded)       this.dataGrid.ExpandDetailsViewAt(this.dataGrid.ResolveToRecordIndex(parentRowIndex));
    //Gets the index of the DetailsView.
    int index = 0;
    foreach (var def in this.dataGrid.DetailsViewDefinition)
    {
        if (def.RelationalColumn == "OrderDetails")
        {
            index = this.dataGrid.DetailsViewDefinition.IndexOf(def);
            index = parentRowIndex + index + 1;
        }
    }           
    //Brings the parent row in the view. 
    var rowcolumnIndex = new RowColumnIndex(index , 1);
    dataGrid.ScrollInView(rowcolumnIndex);
    //Gets the DetailsViewDataGrid by passing the corresponding rowindex and relation name.
    var detailsViewDataGrid = this.dataGrid.GetDetailsViewGrid(this.dataGrid.ResolveToRecordIndex(parentRowIndex), "OrderDetails");
    //Checks whether the given index is currently in view or not.
    //When the specified index is not currently in view, you can bring that row in to the view by using the SfDataGrid.ScrollInView method.
    var firstline = this.dataGrid.GetVisualContainer().ScrollRows.GetVisibleLines().FirstOrDefault(line => line.Region == ScrollAxisRegion.Body);
    var lastline = this.dataGrid.GetVisualContainer().ScrollRows.GetVisibleLines().LastOrDefault(line => line.Region == ScrollAxisRegion.Body);
    if (firstline.LineIndex > index || lastline.LineIndex <= index)
    {               
        //Brings the details view grid in to the view and sets the child grid's SelectedIndex as the ChildRowIndex.
        if (record != null && record.IsExpanded)
        {                
            if (detailsViewDataGrid == null)
            {
                detailsViewManager.BringIntoView(index);
                detailsViewDataGrid = this.dataGrid.GetDetailsViewGrid(this.dataGrid.ResolveToRecordIndex(parentRowIndex), "OrderDetails");
            }                  
        }              
    }
    detailsViewDataGrid.SelectedIndex = childRowIndex;         
}