Learn how to use LINQ in your applications with these code samples, covering the entire range of LINQ functionality and demonstrating LINQ with SQL, DataSets, and XML.

Browse all 101 LINQ Samples

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Introduction

 This sample shows different uses of Element Operators:

• First - Simple
• First - Condition
• FirstOrDefault - Simple
• FirstOrDefault - Condition
• ElementAt

Building the Sample

1. Open the Program.cs
2. Comment or uncomment the desired samples
3. Press Ctrl + F5

Description

First - Simple

(back to top)

This sample uses First to return the first matching element as a Product, instead of as a sequence containing a Product.

public void Linq58()
{
    List<Product> products = GetProductList();

    Product product12 = (
        from p in products
        where p.ProductID == 12
        select p)
        .First();
 
    ObjectDumper.Write(product12);
}

public void Linq58() 
{ 
    List<Product> products = GetProductList(); 
 
    Product product12 = ( 
        from p in products 
        where p.ProductID == 12 
        select p) 
        .First(); 
  
    ObjectDumper.Write(product12); 
}

Result

ProductID=12 ProductName=Queso Manchego La Pastora Category=Dairy Products UnitPrice=38.0000 UnitsInStock=86

First - Condition

(back to top)

This sample uses First to find the first element in the array that starts with 'o'.

public void Linq59()
{
    string[] strings = { "zero", "one", "two", "three", "four", "five", "six", "seven", "eight", "nine" };
 
    string startsWithO = strings.First(s => s[0] == 'o');
 
    Console.WriteLine("A string starting with 'o': {0}", startsWithO);
}

public void Linq59() 
{ 
    string[] strings = { "zero", "one", "two", "three", "four", "five", "six", "seven", "eight", "nine" }; 
  
    string startsWithO = strings.First(s => s[0] == 'o'); 
  
    Console.WriteLine("A string starting with 'o': {0}", startsWithO); 
}

Result

A string starting with 'o': one

FirstOrDefault - Simple

(back to top)

This sample uses FirstOrDefault to try to return the first element of the sequence, unless there are no elements, in which case the default value for that type is returned.

public void Linq61()
 
{
    int[] numbers = { };
 
    int firstNumOrDefault = numbers.FirstOrDefault();
 
    Console.WriteLine(firstNumOrDefault);
}

public void Linq61() 
  
{ 
    int[] numbers = { }; 
  
    int firstNumOrDefault = numbers.FirstOrDefault(); 
  
    Console.WriteLine(firstNumOrDefault); 
}

Result

0

FirstOrDefault - Condition

(back to top)

This sample uses FirstOrDefault to return the first product whose ProductID is 789 as a single Product object, unless there is no match, in which case null is returned.

public void Linq62()
{
    List<Product> products = GetProductList();
 
    Product product789 = products.FirstOrDefault(p => p.ProductID == 789);

    Console.WriteLine("Product 789 exists: {0}", product789 != null);
}

public void Linq62() 
{ 
    List<Product> products = GetProductList(); 
  
    Product product789 = products.FirstOrDefault(p => p.ProductID == 789); 
 
    Console.WriteLine("Product 789 exists: {0}", product789 != null); 
}

Result

Product 789 exists: False

ElementAt

(back to top)

This sample uses ElementAt to retrieve the second number greater than 5 from an array.

public void Linq64()
{
    int[] numbers = { 5, 4, 1, 3, 9, 8, 6, 7, 2, 0 };
 
    int fourthLowNum = (
        from n in numbers
        where n > 5
        select n)
        .ElementAt(1);  // second number is index 1 because sequences use 0-based indexing

    Console.WriteLine("Second number > 5: {0}", fourthLowNum);
}

public void Linq64() 
{ 
    int[] numbers = { 5, 4, 1, 3, 9, 8, 6, 7, 2, 0 }; 
  
    int fourthLowNum = ( 
        from n in numbers 
        where n > 5 
        select n) 
        .ElementAt(1);  // second number is index 1 because sequences use 0-based indexing 
 
    Console.WriteLine("Second number > 5: {0}", fourthLowNum); 
}

Second number > 5: 8

Source Code Files

• Program.cs

101 LINQ Samples

• Restriction Operators
• Projection Operators
• Partitioning Operators
• Ordering Operators
• Grouping Operators
• Set Operators
• Conversion Operators
• Element Operators
• Generation Operators
• Quantifiers
• Aggregate Operators
• Miscellaneous Operators
• Custom Sequence Operators
• Query Execution
• Join Operators

More Information

For more information, see:

• Element Operators Query Expression Syntax Examples (LINQ to DataSet) - http://technet.microsoft.com/en-us/library/bb399382(VS.90).aspx