How to find the Max or the Highest value in (List) No LINQ

Question

In this Method returns the TheQFromDB an Instance from the input list where the property SecondsDiff is the highest and in each item in input has a SecondDiff value but one is the highest . how could i find that without using LINQ ? and how could i check all the items . Look at the Code please

public static TheQFromDB CalculateMaxVal (List<TheQFromDB> input)

{

double maxValue = double.MinValue;

foreach (var item in input)

{

if (item.SecondsDiff > maxValue)

{

maxValue = item.SecondsDiff;

}

}

Console.WriteLine(maxValue);

return null;

}