Check if object can be cast to a certain value type?

Question

I have a Hashtable with results of parsing a certain JSON: decodedJson. decodedJson["key"] can be int, double, float, decimal or a string. I need to convert it to decimal if it's a number (which I plan to do with (decimal)decodedJson["key"]), or handle an error if it's not.

What's the most effective way to determine that?

score 6 · Answer 1 · answered Dec 26 '13 at 14:18

6

if (decodedJson["key"] is decimal)
{
//do your action
}

answered Dec 26 '13 at 14:18

Anarion

2,406
3
28
42

1

Yes, we think alike :) – Sriram Sakthivel Dec 26 '13 at 14:20

score 3 · Answer 2 · edited May 23 '17 at 11:52

Since it can be any numeric type, you might want:

var i = decodedJson["key"];
bool isNumeric = i is byte || i is sbyte || i is short || i is ushort || 
                 i is int || i is uint || i is long || i is ulong || 
                 i is float || i is double || i is decimal;

if (isNumeric)
    Convert.ToDecimal(i);
else
    //handle

If you want to convert it to a type which is not the actual underlying type, a simple cast will not work. Convert class has the comprehensive tests it would need.

Or make it generic all the way if you want:

public static T To<T>(this object source) where T : IConvertible
{
    return (T)Convert.ChangeType(source, typeof(T));
}

public static bool IsNumeric(this Type t)
{
    return t.In(typeof(byte), typeof(sbyte), typeof(short), typeof(ushort), 
                typeof(int), typeof(uint), typeof(long), typeof(ulong), 
                typeof(float), typeof(double), typeof(decimal));
}

public static bool In<T>(this T source, params T[] list)
{
    return list.Contains(source);
}

Or find a more accurate version of IsNumeric here.

So now you call:

var i = decodedJson["key"]; 
if (i.GetType().IsNumeric())
    i.To<decimal>();
else
    //handle

score 2 · Answer 3 · answered Dec 26 '13 at 14:18

2

If the object is decimal you can do this

if (decodedJson["key"] is decimal)
{
   //Your code here
}

answered Dec 26 '13 at 14:18

Sriram Sakthivel

72,067
7
111
189

score 1 · Answer 4 · answered Dec 26 '13 at 14:20

1

The is operator is probably your best choice

http://msdn.microsoft.com/en-us/library/scekt9xw.aspx

    if(decodedJson["key"] is decimal){ 
// do something 
}

answered Dec 26 '13 at 14:20

Austin

754
8
12

score 0 · Answer 5 · answered Dec 26 '13 at 14:19

0

Decimal.TryParse, documentation link below:

http://msdn.microsoft.com/en-us/library/system.decimal.tryparse(v=vs.110).aspx

answered Dec 26 '13 at 14:19

Michael McGriff

793
10
20

score 0 · Answer 6 · answered Dec 26 '13 at 14:51

0

As per the question, if decodedJson["key"] can be anything from int, float, double, decimal or a string. We need to put a check for all types.

if(decodedJson["key"] is int ||  decodedJson["key"] is float || decodedJson["key"] is double || decodedJson["key"] is decimal)
{
     decimal convereted_value = (decimal) decodedJson["key"];
     // Rest of your code here 
}
else
{
     // Error handling code here.
}

answered Dec 26 '13 at 14:51

NiralZaveri

21
2

1

This is again risky considering if the type is `int`, you cant cast to `decimal` type. `Convert` class is the best option. – nawfal Dec 26 '13 at 14:58
May be the Convert class is best option, but you can cast int to decimal, Check out this fiddle http://dotnetfiddle.net/khCkUt – NiralZaveri Dec 26 '13 at 15:09
Niral, of course that is possible. But you cant cast it when the value type is boxed. For instance, try: `object i = 0; decimal d = (decimal)i;` – nawfal Dec 26 '13 at 15:23

Check if object can be cast to a certain value type?

6 Answers6