检查对象是否是 C# 中的数字

Checking if an object is a number in C#

提问by Piotr Czapla

I'd like to check if an object is a number so that .ToString()would result in a string containing digits and +,-,.

我想检查一个对象是否是一个数字，以便.ToString()产生一个包含数字和+,的字符串-，.

Is it possible by simple type checking in .net (like: if (p is Number))?

是否可以通过 .net 中的简单类型检查（例如：）if (p is Number)？

Or Should I convert to string, then try parsing to double?

或者我应该转换为字符串，然后尝试解析为双倍？

Update:To clarify my object is int, uint, float, double, and so on it isn't a string. I'm trying to make a function that would serialize any object to xml like this:

更新：为了澄清我的对象是 int、uint、float、double 等，它不是字符串。我正在尝试创建一个将任何对象序列化为 xml 的函数，如下所示：

<string>content</string>

or

或者

<numeric>123.3</numeric>

or raise an exception.

或引发异常。

采纳答案by Noldorin

You will simply need to do a type check for each of the basic numeric types.

您只需要对每个基本数字类型进行类型检查。

Here's an extension method that should do the job:

这是一个应该完成这项工作的扩展方法：

public static bool IsNumber(this object value)
{
    return value is sbyte
            || value is byte
            || value is short
            || value is ushort
            || value is int
            || value is uint
            || value is long
            || value is ulong
            || value is float
            || value is double
            || value is decimal;
}

This should cover all numeric types.

这应该涵盖所有数字类型。

Update

更新

It seems you do actually want to parse the number from a string during deserialisation. In this case, it would probably just be best to use double.TryParse.

看来您确实想在反序列化期间解析字符串中的数字。在这种情况下，最好使用double.TryParse.

string value = "123.3";
double num;
if (!double.TryParse(value, out num))
    throw new InvalidOperationException("Value is not a number.");

Of course, this wouldn't handle very large integers/long decimals, but if that is the case you just need to add additional calls to long.TryParse/ decimal.TryParse/ whatever else.

当然，这不会处理非常大的整数/长小数，但如果是这样的话，你只需要额外的呼叫添加到long.TryParse/ decimal.TryParse/任何其他。

回答by Peter Lillevold

Yes, this works:

是的，这有效：

object x = 1;
Assert.That(x is int);

For a floating point number you would have to test using the float type:

对于浮点数，您必须使用 float 类型进行测试：

object x = 1f;
Assert.That(x is float);

回答by Philippe Leybaert

Assuming your input is a string...

假设您的输入是一个字符串...

There are 2 ways:

有2种方式：

use Double.TryParse()

使用 Double.TryParse()

double temp;
bool isNumber = Double.TryParse(input, out temp);

use Regex

使用正则表达式

 bool isNumber = Regex.IsMatch(input,@"-?\d+(\.\d+)?");

回答by Martin Liversage

You could use code like this:

你可以使用这样的代码：

if (n is IConvertible)
  return ((IConvertible) n).ToDouble(CultureInfo.CurrentCulture);
else
  // Cannot be converted.

If your object is an Int32, Single, Doubleetc. it will perform the conversion. Also, a string implements IConvertiblebut if the string isn't convertible to a double then a FormatExceptionwill be thrown.

如果你的对象是Int32，Single，Double等它执行转换。此外，一个字符串实现，IConvertible但如果该字符串不能转换为双精度那么 aFormatException将被抛出。

回答by Marc Gravell

There are three different concepts there:

这里有三个不同的概念：

• to check if it isa number (i.e. a (typically boxed) numeric value itself), check the type with is- for example if(obj is int) {...}
• to check if a string could be parsed as a number; use TryParse()
• but if the object isn't a number or a string, but you suspect ToString()might give something that lookslike a number, then callToString()and treat it as a string

• 要检查它是否是数字（即（通常是装箱的）数值本身），请检查类型is- 例如if(obj is int) {...}
• 检查字符串是否可以解析为数字；用TryParse()
• 但是如果对象不是数字或字符串，但您怀疑ToString()可能给出看起来像数字的东西，则调用ToString()并将其视为字符串

In both the first two cases, you'll probably have to handle separately each numeric type you want to support (double/decimal/int) - each have different ranges and accuracy, for example.

在前两种情况下，两个，你可能不得不单独处理您要支持的每个数字类型（double/ decimal/ int） -每个都有不同的范围和精确度，例如。

You could also look at regex for a quick rough check.

您还可以查看正则表达式进行快速粗略检查。

回答by Saul Dolgin

Taken from Scott Hanselman's Blog:

摘自Scott Hanselman 的博客：

public static bool IsNumeric(object expression)
{
    if (expression == null)
    return false;

    double number;
    return Double.TryParse( Convert.ToString( expression
                                            , CultureInfo.InvariantCulture)
                          , System.Globalization.NumberStyles.Any
                          , NumberFormatInfo.InvariantInfo
                          , out number);
}

回答by Kenan E. K.

Take advantage of the IsPrimitive property to make a handy extension method:

利用 IsPrimitive 属性创建一个方便的扩展方法：

public static bool IsNumber(this object obj)
{
    if (Equals(obj, null))
    {
        return false;
    }

    Type objType = obj.GetType();
    objType = Nullable.GetUnderlyingType(objType) ?? objType;

    if (objType.IsPrimitive)
    {
        return objType != typeof(bool) && 
            objType != typeof(char) && 
            objType != typeof(IntPtr) && 
            objType != typeof(UIntPtr);
    }

    return objType == typeof(decimal);
}

EDIT: Fixed as per comments. The generics were removed since .GetType() boxes value types. Also included fix for nullable values.

编辑：根据评论修复。由于 .GetType() 框值类型，因此删除了泛型。还包括可空值的修复。

回答by Joe

If your requirement is really

如果您的要求是真的

.ToString() would result in a string containing digits and +,-,.

.ToString() 将产生一个包含数字和 +,-, 的字符串。

and you want to use double.TryParse then you need to use the overload that takes a NumberStyles parameter, and make sure you are using the invariant culture.

并且您想使用 double.TryParse 那么您需要使用带 NumberStyles 参数的重载，并确保您使用的是不变区域性。

For example for a number which may have a leading sign, no leading or trailing whitespace, no thousands separator and a period decimal separator, use:

例如，对于可能有前导符号、没有前导或尾随空格、没有千位分隔符和句点小数分隔符的数字，请使用：

NumberStyles style = 
   NumberStyles.AllowLeadingSign | 
   NumberStyles.AllowDecimalPoint | 
double.TryParse(input, style, CultureInfo.InvariantCulture, out result);

回答by Mick Bruno

There are some great answers above. Here is an all-in-one solution. Three overloads for different circumstances.

上面有一些很好的答案。这是一个多合一的解决方案。针对不同情况的三种重载。

// Extension method, call for any object, eg "if (x.IsNumeric())..."
public static bool IsNumeric(this object x) { return (x==null ? false : IsNumeric(x.GetType())); }

// Method where you know the type of the object
public static bool IsNumeric(Type type) { return IsNumeric(type, Type.GetTypeCode(type)); }

// Method where you know the type and the type code of the object
public static bool IsNumeric(Type type, TypeCode typeCode) { return (typeCode == TypeCode.Decimal || (type.IsPrimitive && typeCode != TypeCode.Object && typeCode != TypeCode.Boolean && typeCode != TypeCode.Char)); }

回答by satnhak

Rather than rolling your own, the most reliable way to tell if an in-built type is numeric is probably to reference Microsoft.VisualBasicand call Information.IsNumeric(object value). The implementation handles a number of subtle cases such as char[]and HEX and OCT strings.

判断内置类型是否为数字的最可靠方法可能是引用Microsoft.VisualBasic和调用Information.IsNumeric(object value). 该实现处理了许多微妙的情况，例如char[]HEX 和 OCT 字符串。