C# 切换大小写和泛型检查

Switch case and generics checking

提问by Elad Benda

I want to write a function that format intand decimaldifferently into string

我想写一个函数，格式int和decimal不同的字符串

I have this code:

我有这个代码：

and I want to rewrite it to generics:

我想将其重写为泛型：

    public static string FormatAsIntWithCommaSeperator(int value)
    {
        if (value == 0 || (value > -1 && value < 1))
            return "0";
        return String.Format("{0:#,###,###}", value);
    }

    public static string FormatAsDecimalWithCommaSeperator(decimal value)
    {
        return String.Format("{0:#,###,###.##}", value);
    }


    public static string FormatWithCommaSeperator<T>(T value) where T : struct
    {
        string formattedString = string.Empty;

        if (typeof(T) == typeof(int))
        {
            if ((int)value == 0 || (value > -1 && value < 1))
            return "0";

            formattedString = String.Format("{0:#,###,###}", value);
        }

        //some code...
    }

    /// <summary>
    /// If the number is an int - returned format is without decimal digits
    /// </summary>
    /// <param name="value"></param>
    /// <returns></returns>
    public static string FormatNumberTwoDecimalDigitOrInt(decimal value)
    {
        return (value == (int)value) ? FormatAsIntWithCommaSeperator(Convert.ToInt32(value)) : FormatAsDecimalWithCommaSeperator(value);
    }

How can i use T in the function body?

如何在函数体中使用 T ？

What syntax should I use?

我应该使用什么语法？

采纳答案by Nikola Markovinovi?

You might use TypeCodefor switch:

您可以使用TypeCode进行切换：

switch (Type.GetTypeCode(typeof(T)))
{
    case TypeCode.Int32:
       break;
    case TypeCode.Decimal:
       break;
}

回答by SimpleVar

Edit: If you only want to handle exactly int and double, just have two overloads:

编辑：如果您只想精确处理 int 和 double，只需有两个重载：

DoFormat(int value)
{
}

DoFormat(double value)
{
}

---

---

If you insist on using generics:

如果你坚持使用泛型：

switch (value.GetType().Name)
{
    case "Int32":
        break;
    case "Double":
        break;
    default:
        break;
}

OR

或者

if (value is int)
{
    int iValue = (int)(object)value;
}
else if (value is double)
{
    double dValue = (double)(object)value;
}
else
{
}

回答by Adrian Thompson Phillips

Alternatively you could always do:

或者，您可以随时执行以下操作：

public static string FormatWithCommaSeparator<T>(T[] items)
{
    var itemArray = items.Select(i => i.ToString());

    return string.Join(", ", itemArray);
}

回答by Brian

You could check the type of the variabele;

您可以检查变量的类型；

    public static string FormatWithCommaSeperator<T>(T value)
    {
        if (value is int)
        {
            // Do your int formatting here
        }
        else if (value is decimal)
        {
            // Do your decimal formatting here
        }
        return "Parameter 'value' is not an integer or decimal"; // Or throw an exception of some kind?
    }

回答by Paulie Waulie

You could instead of using generics use IConvertible

你可以代替使用泛型使用 IConvertible

    public static string FormatWithCommaSeperator(IConvertible value)
    {
            IConvertible convertable = value as IConvertible;
            if(value is int)
            {
                int iValue = convertable.ToInt32(null);
                //Return with format.
            }
            .....
    }

    public static string FormatWithCommaSeperator(IConvertible value)
    {
            IConvertible convertable = value as IConvertible;
            if(value is int)
            {
                int iValue = convertable.ToInt32(null);
                //Return with format.
            }
            .....
    }

回答by Tamir Daniely

In modern C#:

在现代 C# 中：

public static string FormatWithCommaSeperator<T>(T value) where T : struct
{
    switch (value)
    {
        case int i:
            return $"integer {i}";
        case double d:
            return $"double {d}";
    }
}

回答by flam3

Another way to do switch on generic is:

另一种打开泛型的方法是：

switch (typeof(T))
{
    case Type intType when intType == typeof(int):
        ...
    case Type decimalType when decimalType == typeof(decimal):
        ...
    default:
        ...
}