Building expression tree with multiple OrElse

Question

I am creating a way for users to filter results based on start and end values. An example of this would be:

?RangeColumn=DisplayId&RangeStart=640,830,670&RangeEnd=650,850,680

In this case, the api would return items where the "DisplayId" is between 640-650 or 830-850 or 670-680. My solution works but the query looks pretty bad:

{t => ((((t.DisplayId >= { Item = 640 }.Item) AndAlso (t.DisplayId <= { Item = 650 }.Item)) OrElse ((t.DisplayId >= { Item = 830 }.Item) AndAlso (t.DisplayId <= { Item = 850 }.Item))) OrElse ((t.DisplayId >= { Item = 670 }.Item) AndAlso (t.DisplayId <= { Item = 680 }.Item)))}

The user can have an unlimited number of ranges so this could quickly get crazy really fast so I'm wondering if there is a better way for me to do what I am trying to do. Here are the methods that are relevant to the problem:

private static IQueryable<T> FilterOnRange<T>(Type entityType, RangeProperties rangeProperties, IQueryable<T> query)
 {
 var startCount = rangeProperties.RangeStart.Count();
 var endCount = rangeProperties.RangeEnd.Count();
 if (startCount > 0 || endCount > 0)
 {
 if (startCount != endCount && (startCount > 1 || endCount > 1))
 throw new RangeFilterException();
 }
 else
 return query;
 PropertyInfo pi = GetFilterPropertyInfo(entityType, rangeProperties.RangeColumnName);
 if (pi != null)
 {
 bool propertyIsNullableType = pi.PropertyType.IsGenericType && pi.PropertyType.GetGenericTypeDefinition().Equals(typeof(Nullable<>));
 bool isInteger = pi.PropertyType.Equals(typeof(int)) || (propertyIsNullableType && Nullable.GetUnderlyingType(pi.PropertyType).Equals(typeof(int)));
 bool isDateTimeOffset = pi.PropertyType.Equals(typeof(DateTimeOffset)) || (propertyIsNullableType && Nullable.GetUnderlyingType(pi.PropertyType).Equals(typeof(DateTimeOffset)));
 var maxCount = Math.Max(startCount, endCount);
 ParameterExpression argParam = Expression.Parameter(typeof(T), "t");
 if (isInteger)
 {
 if (maxCount == 1)
 {
 string start = startCount > 0 ? rangeProperties.RangeStart.Single() : null;
 string end = endCount > 0 ? rangeProperties.RangeEnd.Single() : null;
 var lambda = RangeInt<T>(argParam, start, end, rangeProperties.RangeColumnName, propertyIsNullableType);
 query = query.Where(lambda);
 }
 else
 {
 Expression<Func<T, bool>> outerLambda = null;
 for (int i = 0; i < maxCount; i++)
 {
 string start = rangeProperties.RangeStart[i];
 string end = rangeProperties.RangeEnd[i];
 var lambda1 = RangeInt<T>(argParam, start, end, rangeProperties.RangeColumnName, propertyIsNullableType);
 Expression<Func<T, bool>> tempLambda = null;
 i++;
 if (i >= maxCount)
 {
 tempLambda = lambda1;
 }
 else
 {
 start = rangeProperties.RangeStart[i];
 end = rangeProperties.RangeEnd[i];
 var lambda2 = RangeInt<T>(argParam, start, end, rangeProperties.RangeColumnName, propertyIsNullableType);
 var body = Expression.OrElse(lambda1.Body, lambda2.Body);
 tempLambda = Expression.Lambda<Func<T, bool>>(body, lambda1.Parameters[0]);
 }
 if (outerLambda == null)
 outerLambda = tempLambda;
 else
 {
 var body = Expression.OrElse(outerLambda.Body, tempLambda.Body);
 outerLambda = Expression.Lambda<Func<T, bool>>(body, outerLambda.Parameters[0]);
 }
 }
 query = query.Where(outerLambda);
 }
 }
 else if (isDateTimeOffset)
 {
 if (maxCount == 1)
 {
 string start = startCount > 0 ? rangeProperties.RangeStart.Single() : null;
 string end = endCount > 0 ? rangeProperties.RangeEnd.Single() : null;
 var lambda = RangeDateTime<T>(argParam, start, end, rangeProperties.RangeColumnName, propertyIsNullableType);
 query = query.Where(lambda);
 }
 else
 {
 Expression<Func<T, bool>> outerLambda = null;
 for (int i = 0; i < maxCount; i++)
 {
 string start = rangeProperties.RangeStart[i];
 string end = rangeProperties.RangeEnd[i];
 var lambda1 = RangeDateTime<T>(argParam, start, end, rangeProperties.RangeColumnName, propertyIsNullableType);
 Expression<Func<T, bool>> tempLambda = null;
 i++;
 if (i >= maxCount)
 {
 tempLambda = lambda1;
 }
 else
 {
 start = rangeProperties.RangeStart[i];
 end = rangeProperties.RangeEnd[i];
 var lambda2 = RangeDateTime<T>(argParam, start, end, rangeProperties.RangeColumnName, propertyIsNullableType);
 var body = Expression.OrElse(lambda1.Body, lambda2.Body);
 tempLambda = Expression.Lambda<Func<T, bool>>(body, lambda1.Parameters[0]);
 }
 if (outerLambda == null)
 outerLambda = tempLambda;
 else
 {
 var body = Expression.OrElse(outerLambda.Body, tempLambda.Body);
 outerLambda = Expression.Lambda<Func<T, bool>>(body, outerLambda.Parameters[0]);
 }
 }
 query = query.Where(outerLambda);
 }
 }
 else
 throw new InvalidOperationException("Only Datetime and Integer is supported for a range filter.");
 }
 return query;
 }
 private static Expression<Func<T, bool>> RangeInt<T>(ParameterExpression argParam, string start, string end, string columnName, bool propertyIsNullableType)
 {
 int? rangeStart = null;
 int tempRangeStart = int.MinValue;
 if (int.TryParse(start, out tempRangeStart))
 rangeStart = tempRangeStart;
 else
 rangeStart = int.MinValue;
 int? rangeEnd = null;
 int tempRangeEnd = int.MaxValue;
 if (int.TryParse(end, out tempRangeEnd))
 rangeEnd = tempRangeEnd;
 else
 rangeEnd = int.MaxValue;
 if (rangeEnd < rangeStart)
 throw new InvalidOperationException("RangeEnd must be greater than RangeStart.");
 Expression rangeProperty = Expression.Property(argParam, columnName);
 MemberExpression comparisonValue2 = null;
 if (propertyIsNullableType)
 {
 var item = new { Item = (int?)rangeStart };
 var comparisonValue = Expression.Constant(item);
 comparisonValue2 = Expression.MakeMemberAccess(comparisonValue, item.GetType().GetMember("Item").First());
 }
 else
 {
 var item = new { Item = (int)rangeStart };
 var comparisonValue = Expression.Constant(item);
 comparisonValue2 = Expression.MakeMemberAccess(comparisonValue, item.GetType().GetMember("Item").First());
 }
 Expression e1 = Expression.GreaterThanOrEqual(rangeProperty, comparisonValue2);
 MemberExpression comparisonValue4 = null;
 if (propertyIsNullableType)
 {
 var item2 = new { Item = (int?)rangeEnd };
 var comparisonValue3 = Expression.Constant(item2);
 comparisonValue4 = Expression.MakeMemberAccess(comparisonValue3, item2.GetType().GetMember("Item").First());
 }
 else
 {
 var item2 = new { Item = (int)rangeEnd };
 var comparisonValue3 = Expression.Constant(item2);
 comparisonValue4 = Expression.MakeMemberAccess(comparisonValue3, item2.GetType().GetMember("Item").First());
 }
 Expression e2 = Expression.LessThanOrEqual(rangeProperty, comparisonValue4);
 Expression e3 = Expression.AndAlso(e1, e2);
 return Expression.Lambda<Func<T, bool>>(e3, argParam);
 }
 private static Expression<Func<T, bool>> RangeDateTime<T>(ParameterExpression argParam, string start, string end, string columnName, bool propertyIsNullableType)
 {
 DateTimeOffset? rangeStart = null;
 DateTimeOffset tempRangeStart = DateTimeOffset.MinValue;
 if (DateTimeOffset.TryParse(start, out tempRangeStart))
 rangeStart = tempRangeStart;
 else
 rangeStart = DateTimeOffset.MinValue;
 DateTimeOffset? rangeEnd = null;
 DateTimeOffset tempRangeEnd = DateTimeOffset.MaxValue;
 if (DateTimeOffset.TryParse(end, out tempRangeEnd))
 rangeEnd = tempRangeEnd;
 else
 rangeEnd = DateTimeOffset.MaxValue;
 if (rangeEnd < rangeStart)
 throw new InvalidOperationException("RangeEnd must be greater than RangeStart.");
 Expression rangeProperty = Expression.Property(argParam, columnName);
 MemberExpression comparisonValue2 = null;
 if (propertyIsNullableType)
 {
 var item = new { Item = (DateTimeOffset?)rangeStart };
 var comparisonValue = Expression.Constant(item);
 comparisonValue2 = Expression.MakeMemberAccess(comparisonValue, item.GetType().GetMember("Item").First());
 }
 else
 {
 var item = new { Item = (DateTimeOffset)rangeStart };
 var comparisonValue = Expression.Constant(item);
 comparisonValue2 = Expression.MakeMemberAccess(comparisonValue, item.GetType().GetMember("Item").First());
 }
 Expression e1 = Expression.GreaterThanOrEqual(rangeProperty, comparisonValue2);
 MemberExpression comparisonValue4 = null;
 if (propertyIsNullableType)
 {
 var item2 = new { Item = (DateTimeOffset?)rangeEnd };
 var comparisonValue3 = Expression.Constant(item2);
 comparisonValue4 = Expression.MakeMemberAccess(comparisonValue3, item2.GetType().GetMember("Item").First());
 }
 else
 {
 var item2 = new { Item = (DateTimeOffset)rangeEnd };
 var comparisonValue3 = Expression.Constant(item2);
 comparisonValue4 = Expression.MakeMemberAccess(comparisonValue3, item2.GetType().GetMember("Item").First());
 }
 Expression e2 = Expression.LessThanOrEqual(rangeProperty, comparisonValue4);
 Expression e3 = Expression.AndAlso(e1, e2);
 return Expression.Lambda<Func<T, bool>>(e3, argParam);
 }

• svick: Why do you care that the expression tree looks bad?
• GBreen12: I just worry about performance. I don't really care how it looks as long as it performs the same I guess.
• svick: Then you should look at the generated SQL, not the expression tree, that's what affects performance. Also, have you measured the performance? Does it meet your performance goals?

Answer 1

var item = new { Item = (int?)rangeStart };
var comparisonValue = Expression.Constant(item);
comparisonValue2 = Expression.MakeMemberAccess(comparisonValue, item.GetType().GetMember("Item").First());

Creating the anonymous object and then accessing it in the expression doesn't give you anything. You can just use the value directly:

comparisonValue = Expression.Constant(rangeStart, typeof(int?));

• GBreen12: If I change the line to Expression e1 = Expression.GreaterThanOrEqual(rangeProperty, Expression.Constant(rangeStart)); It throws an error if the field is nullable
• svick: In that case, I think Expression.Constant(rangeStart, typeof(int?)) should work.