Convert.ToString ()과 .ToString ()의 차이점

Convert.ToString ()과 .ToString ()의 차이점

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차이점은 무엇이며 Convert.ToString()그리고 .ToString()?

온라인에서 많은 차이점을 발견했지만 주요 차이점은 무엇입니까?

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Convert.ToString()처리 null하지만 ToString()그렇지 않습니다.

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ToString()객체를 호출 하면 객체가 null이 아닌 것으로 가정합니다 (인스턴스 메소드를 호출하려면 객체가 있어야하기 때문에). Convert.ToString(obj)객체가 null이 아니라고 가정 할 필요는 없지만 (Convert 클래스의 정적 메서드 String.Empty이므로 ) null 인 경우 반환 됩니다 .

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null값 처리에 대한 다른 답변 외에도 base를 호출하기 전에 Convert.ToString사용 IFormattable및 IConvertible인터페이스를 시도하십시오 Object.ToString.

예:

class FormattableType : IFormattable
{
    private double value = 0.42;

    public string ToString(string format, IFormatProvider formatProvider)
    {
        if (formatProvider == null)
        {
            // ... using some IOC-containers
            // ... or using CultureInfo.CurrentCulture / Thread.CurrentThread.CurrentCulture
            formatProvider = CultureInfo.InvariantCulture;
        }

        // ... doing things with format
        return value.ToString(formatProvider);
    }

    public override string ToString()
    {
        return value.ToString();
    }
}

결과:

Convert.ToString(new FormattableType()); // 0.42
new FormattableType().ToString();        // 0,42

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이 예제를 통해 차이점을 이해하십시오.

int i= 0;
MessageBox.Show(i.ToString());
MessageBox.Show(Convert.ToString(i));

우리는 정수를 변환 할 수 있습니다 i사용 i.ToString ()하거나 Convert.ToString. 차이점은 무엇입니까?

이들의 기본적인 차이점은 Convert함수가 NULLS를 처리하지만 i.ToString ()그렇지 않은 경우 NULLS를 처리 한다는 것입니다 . NULL 참조 예외 오류가 발생합니다. 따라서 올바른 코딩 방법 convert은 항상 안전합니다.

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클래스를 만들고 toString메소드를 재정 의하여 원하는 작업을 수행 할 수 있습니다.

예를 들어 "MyMail" 클래스를 만들고 toString전자 메일을 보내거나 현재 개체를 쓰는 대신 다른 작업을 수행 하도록 메서드를 재정의 할 수 있습니다 .

는 Convert.toString동등한 지정된 값을 문자열 표현으로 변환한다.

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object o=null;
string s;
s=o.toString();
//returns a null reference exception for string  s.

string str=convert.tostring(o);
//returns an empty string for string str and does not throw an exception.,it's 
//better to use convert.tostring() for good coding

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null 처리를 제외하고 는 메소드는 "기본적으로"동일 합니다.

Pen pen = null; 
Convert.ToString(pen); // No exception thrown
pen.ToString(); // Throws NullReferenceException

From MSDN :
Convert.ToString Method

Converts the specified value to its equivalent string representation.

Object.ToString

Returns a string that represents the current object.

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In Convert.ToString(), the Convert handles either a NULL value or not but in .ToString() it does not handles a NULL value and a NULL reference exception error. So it is in good practice to use Convert.ToString().

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For Code lovers this is the best answer.

    .............. Un Safe code ...................................
    Try
        ' In this code we will get  "Object reference not set to an instance of an object." exception
        Dim a As Object
        a = Nothing
        a.ToString()
    Catch ex As NullReferenceException
        Response.Write(ex.Message)
    End Try


    '............... it is a safe code..............................
    Dim b As Object
    b = Nothing
    Convert.ToString(b)

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I agree with @Ryan's answer. By the way, starting with C#6.0 for this purpose you can use:

someString?.ToString() ?? string.Empty;

or

$"{someString}"; // I do not recommend this approach, although this is the most concise option.

instead of

Convert.ToString(someString);

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ToString() can not handle null values and convert.ToString() can handle values which are null, so when you want your system to handle null value use convert.ToString().

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Convert.ToString(strName) will handle null-able values and strName.Tostring() will not handle null value and throw an exception.

So It is better to use Convert.ToString() then .ToString();

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ToString() Vs Convert.ToString()

Similarities :-

Both are used to convert a specific type to string i.e int to string, float to string or an object to string.

Difference :-

ToString() can't handle null while in case with Convert.ToString() will handle null value.

Example :

namespace Marcus
{
    class Employee
    {
        public int Id { get; set; }
        public string Name { get; set; }
    }
    class Startup
    {
        public static void Main()
        {
            Employee e = new Employee();
            e = null;

            string s = e.ToString(); // This will throw an null exception
            s = Convert.ToString(e); // This will throw null exception but it will be automatically handled by Convert.ToString() and exception will not be shown on command window.
        }
    }
}

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To understand both the methods let's take an example:

int i =0;
MessageBox.Show(i.ToString());
MessageBox.Show(Convert.ToString(i)); 

Here both the methods are used to convert the string but the basic difference between them is: Convert function handles NULL, while i.ToString() does not it will throw a NULL reference exception error. So as good coding practice using convert is always safe.

Let's see another example:

string s;
object o = null;
s = o.ToString(); 
//returns a null reference exception for s. 

string s;
object o = null;
s = Convert.ToString(o); 
//returns an empty string for s and does not throw an exception.

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Convert.ToString(value) first tries casting obj to IConvertible, then IFormattable to call corresponding ToString(...) methods. If instead the parameter value was null then return string.Empty. As a last resort, return obj.ToString() if nothing else worked.

It's worth noting that Convert.ToString(value) can return null if for example value.ToString() returns null.

See .Net reference source

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i wrote this code and compile it.

class Program
{
    static void Main(string[] args)
    {
        int a = 1;
        Console.WriteLine(a.ToString());
        Console.WriteLine(Convert.ToString(a));
    }
}

by using 'reverse engineering' (ilspy) i find out 'object.ToString()' and 'Convert.ToString(obj)' do exactly one thing. infact 'Convert.ToString(obj)' call 'object.ToString()' so 'object.ToString()' is faster.

Object.ToString Method:

class System.Object
{
    public string ToString(IFormatProvider provider)
    {
        return Number.FormatInt32(this, null, NumberFormatInfo.GetInstance(provider));
    }
}

Conver.ToString Method:

class System.Convert
{
    public static string ToString(object value)
    {
        return value.ToString(CultureInfo.CurrentCulture);
    }
}

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Convert.Tostring() function handles the NULL whereas the .ToString() method does not. visit here.

참고URL : https://stackoverflow.com/questions/2828154/difference-between-convert-tostring-and-tostring