selecting min and max values while avoiding multiple enumerations.

gistfile1.cs

var tests = dbTests.Select(t => new TestSearchable
{
    Price = t.LabTests.Select(l => l.ListPrice)
                           .GroupBy(l => 0)
                           .Select(l => new Dictionary<string, int>
                                {
                                    { "High", l.Max() },
                                    { "Low", l.Min() }
                                }).First(),
    TurnAround = t.LabTests.SelectMany(l => new[] { l.EstimatedTatLow, l.EstimatedTatHigh })
                           .GroupBy(l => 0)
                           .Select(l => new Dictionary<string, int>
                                {
                                    { "High", l.Max() },
                                    { "Low", l.Min() }
                                }).First(),

    // ...

}.PopulateWith(t));

gistfile2.cs

var tests = dbTests.Select(t => new TestSearchable
{
    Price = new Dictionary<string, int>
                        {
                            { "High", t.LabTests.Max(l => l.ListPrice) },
                            { "Low", t.LabTests.Min(l => l.ListPrice) }
                        },
    TurnAround = new Dictionary<string, int>
        {
            { "High", t.LabTests.SelectMany(l => new[] { l.EstimatedTatLow, l.EstimatedTatHigh }).Max() },
            { "Low", t.LabTests.SelectMany(l => new[] { l.EstimatedTatLow, l.EstimatedTatHigh }).Min() }
        },

    // ...

}.PopulateWith(t));