How can I combine (n) expressions using LINQ?

Question

I have a grid with (n) dynamically generated columns. One of the requirements is that a row only be shown in the grid if a non-null/non-zero value exists in one of the shown columns. I am using an Infragistics XamGrid, which has the option to use a row filter that will accept an expression as its filter criteria. I have bound the Key of my columns to MyObject properties.

I am trying to generate a chain of expressions based on which columns in my grid are shown. Here is some pseudo-code that shows an idea what I'm trying to accomplish

System.Linq.Expressions.Expression<Func<MyObject, bool>> expr = product =>
{
    foreach (var p in MyGrid.Columns.Where(co => co.DataType == typeof (decimal?) && co.Visibility == Visibility.Visible))
    {
        Expression<Func<MyObject, bool>> exprInner = lrnc => ((decimal?) lrnc.GetPropValue(p.Key)) != 0.0m;
        combined = System.Linq.Expressions.Expression.OrElse(combined.Body, exprInner.Body);
    }
};

Like this? albahari.com/nutshell/predicatebuilder.aspx

hatchet - done with SOverflow
– hatchet - done with SOverflow

2017-06-12 18:36:57 +00:00
Commented Jun 12, 2017 at 18:36 — hatchet - done with SOverflow
– hatchet - done with SOverflow, Commented Jun 12, 2017 at 18:36
@hatchet Thanks, that gave me all the info I needed.

dev30207
– dev30207

2017-06-13 17:31:06 +00:00
Commented Jun 13, 2017 at 17:31 — dev30207
– dev30207, Commented Jun 13, 2017 at 17:31

dev30207 · Accepted Answer · 2017-06-13 17:30:01Z

Big thanks to hatchet and his link. I was able to dynamically combine expressions based on reflected properties to create a RowsFilter for my XamGrid.

private RowsFilter m_rowsFilter;

private void CreateFilter()
{
    CustomComparisonCondition c = new CustomComparisonCondition();

    var predicate = PredicateBuilder.False<LineRatingNodeComparison>();
    foreach (string colKey in MyXamGrid.Columns.Where(co => co.DataType == typeof (decimal?) && co.Visibility == Visibility.Visible).Select(co => co.Key))
    {
        string tempKey = colKey;
        predicate = predicate.Or(p => p.GetPropValue(tempKey) != null && (decimal?) p.GetPropValue(tempKey) != 0.0m);
    }
    c.Expression = predicate;

    //Add the RowsFilter to one column that always exists on the grid.
    m_rowsFilter = new RowsFilter(typeof (MyObject), MyXamGrid.Columns.DataColumns["Company"]);
    m_rowsFilter.Conditions.Add(c);
    MyXamGrid.FilteringSettings.RowFiltersCollection.Add(m_rowsFilter);
}

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