C# | String Concat with examples | Set-1

Last Updated : 01 Feb, 2019

String.Concat Method is used to concatenate one or more instances of String or the String representations of the values of one or more instances of Object. It always returns a concatenated string.
This method can be overloaded by passing different types and number of parameters to it. There are total 11 methods in the overload list of the Concat method in which 3 are discussed in this article and remaining are discussed in Set-2, Set-3, and Set-4.

Concat(String, String, String, String)
Concat(Object, Object, Object, Object)
Concat(Object, Object, Object)
Concat(String, String)
Concat(String, String, String)
Concat(String[])
Concat(Object[])
Concat(Object)
Concat(Object, Object)
Concat(IEnumerable<String>)
Concat<T>(IEnumerable<T>)

1. Concat(String, String, String, String)

This method is used to concatenate four different string into a single string. You can also use Concatenation operator(+)to concatenate strings.

Note: If an array contains a null object, then the Empty string is used in place of a null object.

Syntax:

public static string Concat (string strA, string strB, string strC, string strD);

Parameters:

strA: First string to concatenate.
strB: Second string to concatenate.
strC: Third string to concatenate.
strD: Fourth string to concatenate.
The type of all these parameters is System.String.

Return Value: The return type of this method is System.String. This method returns a string which is created from the concatenation of four strings, i.e. strA, strB, strC, and strD.

Example:

// C# program to illustrate the use of  
// Concat(String, String, String, String) Method 
using System; 
  
class GFG { 
      
    // Main Method 
    static public void Main() 
    { 
        string strA = "Welcome "; 
        string strB = "to "; 
        string strC = "GFG "; 
        string strD = "Portal."; 
        string str; 
  
        // print all strings 
        Console.WriteLine("String A is: {0}", strA); 
        Console.WriteLine("String B is: {0}", strB); 
        Console.WriteLine("String C is: {0}", strC); 
        Console.WriteLine("String D is: {0}", strD); 
  
        // Concatenate four different strings 
        // into a single String using the  
        // Concat(String, String, String, String) Method 
        str = String.Concat(strA, strB, strC, strD); 
  
        Console.WriteLine("Concatenated string is: {0}", str); 
    } 
} 

Output:

String A is: Welcome 
String B is: to 
String C is: GFG 
String D is: Portal.
Concatenated string is: Welcome to GFG Portal.

2. Concat(Object, Object, Object, Object)

This method is used to concatenate the string representations of four specified objects and any objects specified in an optional variable length parameter list.

Note: If a null argument is present in this method then String.Empty is used in place of a null argument.

Syntax:

public static string Concat (object argA, object argB, object argC, object argD);

Parameters:

argA: First object to concatenate.
argB: Second object to concatenate.
argC: Third object to concatenate.
argD: Fourth object to concatenate.

Return Value: The return type of this method is System.String. It returns the concatenated string which is the representation of each value present in the parameter list.

Example:

// C# program to illustrate the use of  
// Concat(object, object, object, object) Method 
using System; 
  
class GFG { 
      
    // Main method 
    public static void Main() 
    { 
  
        // string 
        string strA = "Hello! "; 
  
        // object 
        object ob = strA; 
  
        // object array 
        Object[] objs = new Object[] {"Black", " Blue"}; 
  
        // Concatenating four objects by using the 
        // Concat(object, object, object, object) method 
        Console.WriteLine("Concatenate four objects: {0}", 
                             String.Concat(ob, ob, ob, ob)); 
                               
        Console.WriteLine("Concatenate two element object array: {0}",  
                                                String.Concat(objs)); 
    } 
} 

Output:

Concatenate four objects: Hello! Hello! Hello! Hello! 
Concatenate two element object array: Black Blue

3. Concat(Object, Object, Object)

This method is used to concatenates the string representations of three specified objects. If a null argument is present in this method then String.Empty is used in place of null argument.

Syntax:

public static string Concat (object argA, object argB, object argC);

Note: The method concatenates argA, argB, and argC by calling the parameterless ToString method of each object and it does not add any delimiters.

Parameters:

argA: First object to concatenate.
argB: Second object to concatenate.
argC: Third object to concatenate.

Return Value: The return type of this method is System.String. This method returns a concatenated string, which is the representation of each value present in the parameter list.

Example:

// C# program to illustrate the use of  
// Concat(object, object, object) Method 
using System; 
  
class GFG { 
      
    // Main method 
    public static void Main() 
    { 
  
        // string 
        string strA = "GFG "; 
  
        // object 
        object ob = strA; 
  
        // Concatenating three objects by using 
        // Concat(object, object, object) method 
        Console.WriteLine("Concatenate three objects : {0}", 
                                 String.Concat(ob, ob, ob)); 
    } 
} 