6 Effective Ways To Concatenate Strings In C#

// Simple string concatenation     
Console.WriteLine("Hello" + " " + "String " + "!");

// Declare strings    
string firstName = "Mahesh";    
string lastName = "Chand";    
    
// Concatenate two string variables    
string name = firstName + " " + lastName;    
Console.WriteLine(name);

// String Interpolation    
string author = "Mahesh Chand";    
string book = "C# Programming";    
// Use string interpolation to concatenate strings.    
string bookAuthor = $"{author} is the author of {book}.";    
Console.WriteLine(bookAuthor);

// String.Concat method    
string fName = "Mahesh";    
string lName = "Chand";    
string Name = string.Concat(fName, lName); 

// Concatenate Concat    
string Name3 = string.Concat(string.Concat(fName, lName), "Beniwal");

// Concatenate an array of strings    
string[] authors = { "Mahesh Chand ", "Chris Love ", "Dave McCarter ", "Praveen Kumar "};    
    
// Concatenate all strings of an array into one string    
string arrayStr = string.Concat(authors);    
Console.WriteLine(arrayStr);

// Concatenate a string and an array of strings    
string strArrStr = string.Concat("Authors: ", authors);    
Console.WriteLine(strArrStr);

// Using String.Join(String, String[])    
int[] intArray = { 1, 3, 5, 7, 9 };    
String seperator = ", ";    
string result = "Int, ";    
result += String.Join(seperator, intArray);    
Console.WriteLine($"Result: {result}");    

Listing 7.

The following code example in Listing 8 concatenates an array element separated by a separator. The second and third parameters of String.The join method specifies the starting index of the array to start joining the number of elements in the array.

// Using String.Join(String, String[], int int)    
// Let's concatenate first two strings of the array    
String[] arr2 = { "Mahesh Chand ", "Chris Love ", "Dave McCarter ", "Praveen Kumar " };    
String seperator2 = ", ";    
string result2 = "First Author, ";    
result2 += String.Join(seperator2, arr2, 1, 2);    
Console.WriteLine($"Result: {result2}");

Listing 8.

5. Concatenate string using String.Format method in C#

String.Format() method formats strings in a desired format by inserting objects and variables with specified space and alignments into other strings and literals. It is also often used to format strings into specific formats.

String.Format() method has eight overloaded formats to provide options to format various objects and variables that allow various variables to format strings.

Note: In C# 6 or later versions, String Interpolation is recommended. Sting interpolation is more flexible and more readable and can achieve the same results without composite formatting.

Insert a single object in a string.

We can insert one or more objects and expressions in a string at a specified position using the String.Format method. The position in the string starts at the 0th index.

For a single object formatting, the first argument is the format, and the second argument is the value of the object. The object is replaced at the {0} position in the string.

public static string Format (string format, object arg0);

The following code example in Listing 9 inserts a DateTime object in an existing string format.

/* *** Simple String.Format **/    
string date = String.Format("Today's date is {0}", DateTime.Now);    
Console.WriteLine(date);

Listing 9.

As you can see from the above code example, {0} is at the last portion in the string, and the second argument is a DateTime.Now. In this case, string portion {0} will be replaced by the value of DateTime.Now, in the string. Figure 2 is the result of the above code.

Figure 2.

Insert multiple objects in a string.

We can insert multiple objects or expressions in a string to give it a desired format. The following code example in Listing 10 creates a string by inserting five objects.

/* *** String.Format with multiple objects **/    
string author = "Mahesh Chand";    
string book = "Graphics Programming with GDI+";    
int year = 2003;    
decimal price = 49.95m;    
string publisher = "APress";    
    
// Book details    
string bookDetails = String.Format("{0} is the author of book {1} \n " +    
"published by {2} in year {3}. \n Book price is ${4}. ",    
author, book, publisher, year, price);    
Console.WriteLine(bookDetails);

Listing 10.

As you can see from the above code example, the String.Format has placeholders for objects, starting at the 0th to the 4th index. The {0} is replaced by the first object passed in the method, {1} is replaced by the second object passed in the method, and so on.

The output of Listing 10 generates Figure 3.

Figure 3.

6. StringBuilder.Append method in C#

String object in .NET is immutable. What does that mean? It means every time you use one of the String class methods, no matter if you use the same variable or a new variable, a new string object is created in memory. That means a memory space is allocated for that new string in your computer memory. The more string methods you use to manipulate strings, the more memory space will be allocated in memory. That means in a string manipulation-heavy code, if strings are not used wisely, it could lead to some serious app performance issues.

.NET provides the System.Text.StringBuilder class that can be used to modify strings without creating new string objects. StringBuilder is highly recommended if you have more than a few hundred string concatenation operations in your code. StringBuilder is not recommended for a few string concatenation operations.

StringBuilder class is defined in the System.Text namespace. You must either import this namespace in your class or reference it directly in the object instantiation.

using System.Text;

StringBuilder constructor can take a string or can be no arguments.

The following code snippet creates a StringBuilder and appends three strings.

System.Text.StringBuilder builder = new System.Text.StringBuilder("Mahesh Chand");    
builder.Append(", ");    
builder.Append("Chris Love");    
builder.Append(", Praveen Kumar");

The following code example creates a string of numbers from 0 to 999, and a comma and a space separate each number.

System.Text.StringBuilder numbers = new System.Text.StringBuilder();    
// Create a string of 1000 numbers from 0 to 999    
// separated by a comma and space    
for (int counter = 0; counter <= 999; counter++)    
{    
numbers.Append(counter);    
numbers.Append(", ");    
}    
Console.WriteLine(numbers);

The output of the above code looks like Figure 4.

Figure 4.

Summary

C# and .NET provide various options to concatenate strings. In the code examples listed in this article, we saw how to use these options to concatenate strings.

Continue reading more, Most Common C# String Code Examples.