/// <summary>
/// Gets the expression.
/// </summary>
/// <param name="entityType">Type of the entity.</param>
/// <param name="serviceInstance">The service instance.</param>
/// <param name="parameterExpression">The parameter expression.</param>
/// <param name="selection">The selection.</param>
/// <returns></returns>
public override Expression GetExpression(Type entityType, IService serviceInstance, ParameterExpression parameterExpression, string selection)
{
var values = selection.Split('|');
ComparisonType comparisonType = values[0].ConvertToEnum <ComparisonType>(ComparisonType.EqualTo);
decimal? amountValue = values[1].AsDecimalOrNull();
var qry = new BenevolenceRequestService((RockContext)serviceInstance.Context).Queryable();
var totalAmountEqualQuery = qry.Where(p => p.BenevolenceResults.Sum(a => a.Amount) == amountValue);
BinaryExpression compareEqualExpression = FilterExpressionExtractor.Extract <Rock.Model.BenevolenceRequest>(totalAmountEqualQuery, parameterExpression, "p") as BinaryExpression;
BinaryExpression result = FilterExpressionExtractor.AlterComparisonType(comparisonType, compareEqualExpression, null);
return(result);
}