GetProperty() to get minimum/maximum value of numbers returns null

Question

I am trying to write a code that outputs the details of a number type (int, uint, ...) in C# (MinValue, MaxValue, sizeof, name).

This is the code I wrote so far:

Console.WriteLine(new string('-', 120));
Console.WriteLine("{0,-10} {1,-20} {2,40} {3,40}",
    "Type", "Byte(s) of memory", "Min", "Max");
Console.WriteLine(new string('-', 120));
Type[] types = new Type[] {
    typeof(byte),
    typeof(sbyte),
    typeof(int),
    typeof(uint),
    typeof(short),
    typeof(ushort),
    typeof(long),
    typeof(ulong),
    typeof(Int128),
    typeof(UInt128),
    typeof(Half),
    typeof(float),
    typeof(double),
    typeof(decimal),
};

int[] typesSizes = new int[]
{
    sizeof(System.Byte),
    sizeof(sbyte),
    sizeof(int),
    sizeof(uint),
    sizeof(short),
    sizeof(ushort),
    sizeof(long),
    sizeof(ulong),
    sizeof(Int128),
    sizeof(UInt128),
    sizeof(Half),
    sizeof(float),
    sizeof(double),
    sizeof(decimal),
};

dynamic instance;
int size;
Type type;

for (int i = 0; i < typesSizes.Length; i++)
{
    size = typesSizes[i];
    type = types[i];

    instance = Activator.CreateInstance(type);

    if (instance == null)
    {
        throw new NullReferenceException();
    }
    
    var minValue = type.GetProperty("MinValue")?.GetValue(instance);// here it returns null for built-in types
    var maxValue = type.GetProperty("MaxValue")?.GetValue(instance);

    Console.WriteLine("{0,-10} {1,-20} {2,40} {3,40}",
    type.Name, size, minValue, maxValue);
}

I don't know why - but it returns null for the built-in number types.

I know I can solve this problem much easier by just creating 4 arrays and copying pasting the properties. But I want to know why/how this happens.

Answer 1

Your code is mostly correct, but for primitive integer types, MinValue and MaxValue are (constant) fields, not properties.

So, for int, float etc. it must be GetField instead of GetProperty:

var minValue = type.GetField("MinValue")?.GetValue(instance);
var maxValue = type.GetField("MaxValue")?.GetValue(instance);