C# Object.ToString
last modified July 5, 2023
C# Object.ToString tutorial shows how to use Object.ToString method in C#.
The Object.ToString returns a string that represents the current
object. It is the main formatting method in .NET. The default implementation
of the method returns the fully qualified name of the object's type.
Passing an object to the Console.WriteLine method, the
Object.ToString method is called.
There are multiple challenges when converting types into strings. For instance, the string output may be culture specific, as seen in dates and times. Or the internal implementation of the type differs from the user expected format.
Custom types often override the default implementation of the
Object.ToString method. In addition, it is possible to overload
the method. For maximum flexibility, we can also provide our own formatter
objects.
C# default ToString
The default ToString method returns the fully qualified name of
the type.
var u1 = new User("John Doe", "gardener");
var u2 = new User("Roger Roe", "driver");
Console.WriteLine(u1);
Console.WriteLine(u2);
class User
{
private string Name {get; set; }
private string Occupation {get; set;}
public User(string Name, string Occupation) =>
(this.Name, this.Occupation) = (Name, Occupation);
}
We have a User class which has not overriden the
ToString method; it uses the default one from its parent.
Console.WriteLine(u1);
The ToString method is called when we pass the object to the
Console.WriteLine method.
$ dotnet run User User
C# override ToString
In the next example, we override the ToString method.
var u1 = new User("John Doe", "gardener");
var u2 = new User("Roger Roe", "driver");
Console.WriteLine(u1);
Console.WriteLine(u2);
class User
{
private string Name {get; set; }
private string Occupation {get; set;}
public User(string Name, string Occupation) =>
(this.Name, this.Occupation) = (Name, Occupation);
public override string ToString()
{
return $"User {{ {Name} {Occupation} }}";
}
}
The overriden ToString method returns the user's name and
occupation, giving a more meaningful output.
$ dotnet run
User { John Doe gardener }
User { Roger Roe driver }
C# record ToString
The record type provides a default implementation of the
ToString method with additional information about the attributes of
the object.
var u1 = new User("John Doe", "gardener");
var u2 = new User("Roger Roe", "driver");
Console.WriteLine(u1);
Console.WriteLine(u2);
record User(string Name, string Occupation);
In this example, we use a record instead of a class.
$ dotnet run
User { Name = John Doe, Occupation = gardener }
User { Name = Roger Roe, Occupation = driver }
C# DateTime ToString
Formatting datetime data is complex; not only multiple cultures have different standards for displaying date and time, each culture may have multiple ways for displaying date and time.
The DateTime time has a default ToString method and
a few additional built-in format methods. In addition, it also allows to provide
our own formats.
using System.Globalization;
Console.OutputEncoding = System.Text.Encoding.UTF8;
var d1 = DateTime.Now;
Console.WriteLine(d1);
string fmt = "MMMM dd, yyyy (dddd)";
var d2 = new DateTime(2020, 5, 20);
Console.WriteLine(d2.ToString(fmt));
var d3 = new DateTime(2021, 3, 30);
Console.WriteLine(d3.ToShortDateString());
DateTime now = DateTime.Now;
CultureInfo ci = new CultureInfo("sk-SK");
Console.WriteLine($"Dnešný dátum a čas: {now.ToString("F", ci)}");
In the example, we use a default DateTime formatter, a custom one,
a built-in one, and a culture specific one.
$ dotnet run 4/8/2021 1:14:43 PM May 20, 2020 (Wednesday) 3/30/2021 Dnešný dátum a čas: štvrtok 8. apríla 2021 13:14:43
C# ToString with monetary data
Formatting monetary data is also complex. Countries use different decimal separators and currrency symbols. Also, the currencty symbol can be placed in the front or in the back of the value.
using System.Globalization;
decimal val = 766.45m;
Console.WriteLine(val.ToString("C3", new CultureInfo("en-US")));
Console.WriteLine(val.ToString("C3", new CultureInfo("fr-FR")));
Console.WriteLine(val.ToString("C3", new CultureInfo("zh-CN")));
Console.WriteLine(val.ToString("C3", new CultureInfo("sk-SK")));
Console.WriteLine(val.ToString("C3", new CultureInfo("ja-JP")));
The example uses the C3 currency specifier with five different
cultures.
$ dotnet run $766.450 766,450 € ¥766.450 766,450 € ￥766.450
C# overloaded ToString
In the following example, we overload the ToString method.
var t1 = new Temperature(0m);
Console.WriteLine(t1.ToString());
Console.WriteLine(t1.ToString(Temperature.Scale.Celsius));
Console.WriteLine(t1.ToString(Temperature.Scale.Kelvin));
Console.WriteLine(t1.ToString(Temperature.Scale.Fahrenheit));
Console.WriteLine("--------------------");
var t2 = new Temperature(-20m);
Console.WriteLine(t2.ToString());
Console.WriteLine(t2.ToString(Temperature.Scale.Celsius));
Console.WriteLine(t2.ToString(Temperature.Scale.Kelvin));
Console.WriteLine(t2.ToString(Temperature.Scale.Fahrenheit));
Console.WriteLine("--------------------");
var t3 = new Temperature(32m);
Console.WriteLine(t3.ToString());
Console.WriteLine(t3.ToString(Temperature.Scale.Celsius));
Console.WriteLine(t3.ToString(Temperature.Scale.Kelvin));
Console.WriteLine(t3.ToString(Temperature.Scale.Fahrenheit));
class Temperature
{
private decimal temp;
public Temperature(decimal temp)
{
this.temp = temp;
}
public decimal Celsius
{
get { return this.temp; }
}
public decimal Kelvin
{
get { return this.temp + 273.15m; }
}
public decimal Fahrenheit
{
get { return Math.Round(((decimal)(this.temp * 9 / 5 + 32)), 2); }
}
public override string ToString()
{
return this.ToString(Scale.Celsius);
}
public string ToString(Scale scale)
{
var res = scale switch
{
Scale.Celsius => this.Celsius.ToString("N2") + " °C",
Scale.Fahrenheit => this.Fahrenheit.ToString("N2") + " °F",
Scale.Kelvin => this.Kelvin.ToString("N2") + " K",
_ => throw new FormatException($"Unsupported scale: '{scale}'")
};
return res;
}
internal enum Scale
{
Celsius,
Kelvin,
Fahrenheit
}
}
We have a Temperature type. It can be expressed in Celsius,
Fahrenheit, or Kelvin scales. We have an overloaded ToString method
which formats the temperature based on the provided scale.
public override string ToString()
{
return this.ToString(Scale.Celsius);
}
The override method calls the second method, passing it the
Scale.Celsius.
var res = scale switch
{
Scale.Celsius => this.Celsius.ToString("N2") + " °C",
Scale.Fahrenheit => this.Fahrenheit.ToString("N2") + " °F",
Scale.Kelvin => this.Kelvin.ToString("N2") + " K",
_ => throw new FormatException($"Unsupported scale: '{scale}'")
};
A switch expression is used to format the temperature value, based on the given scale.
$ dotnet run 0.00 °C 0.00 °C 273.15 K 32.00 °F -------------------- -20.00 °C -20.00 °C 253.15 K -4.00 °F -------------------- 32.00 °C 32.00 °C 305.15 K 89.60 °F
Source
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