I am using to build a set of functions that will allow me to build complex queries within Linq. So far I have the following code:

private IQueryable BuildSampleEntityInt(params int\[\] values)
{
    return values.Select(
           value =>
           new SampleEntityInt() { SampleSearchKey = value }).AsQueryable();
}

public static IQueryable Between(this IQueryable source, Expression\> keySelector, TKey low, TKey high, bool inclusive = true) where TKey : IComparable
{
    var key = Expression.Invoke(keySelector, keySelector.Parameters.ToArray());

    var intLow = int.Parse(low.ToString());
    var intHigh = int.Parse(high.ToString());

    var lowerBound = (inclusive)
              ? Expression.GreaterThanOrEqual(key, Expression.Constant(intLow, typeof(int)))
              : Expression.GreaterThan(key, Expression.Constant(intLow, typeof(int)));

    var upperBound = (inclusive)
              ? Expression.LessThanOrEqual(key, Expression.Constant(intHigh, typeof(int)))
              : Expression.LessThan(key, Expression.Constant(intHigh, typeof(int)));

    var and = Expression.AndAlso(lowerBound, upperBound);
    var lambda = Expression.Lambda\>(
                    and, keySelector.Parameters);

    return source.Where(lambda);
}

private IQueryable BuildSampleEntityInt(params int\[\] values)
{
    return values.Select(
           value =>
           new SampleEntityInt() { SampleSearchKey = value }).AsQueryable();
}

If I use the following code

 lowValue = 2;
 highValue = 11;

 var sampleData = BuildSampleEntityInt(1, 3, 10, 11, 12, 15);
 var query = sampleData.Between(s => s.SampleSearchKey, lowValue, highValue, false);
 Assert.AreEqual(2, query.Count());

All is well, but if I use:

lowValueString = "3";
highValueString = "10";

var sampleData = BuildSampleEntityInt(1, 3, 10, 11, 12, 15);
var query = sampleData.Between(s => s.SampleSearchKey, lowValueString , highValueString);
Assert.AreEqual(2, query.Count());

The code crashes because the methods; GreaterThan, LessThan, GreaterThanOrEqual and LessThanOrEqual of an Expression does not work with Strings.