How to use Lambda Expression in C#

Let us see some practical examples where lambda expressions can be used in C#.

Scenario 1

Imagine a scenario where a list of strings holds certain data which needs to be displayed in comma-separated format. With Lambda expressions it is simple to achieve it.

var data = new List<string> 
{ 
    "One", 
    "Two", 
    "Three", 
    "Four", 
    "Five" 
}; 
var result = String.Join(", ", data.Select(x => x));

The result will be — “One, Two, Three, Four, Five”

Scenario 2

Imagine a scenario, where a list of strings is present, and we need to prefix it with some data to process it together. Let’s see how to achieve this using lambda expression.

var data = new List<PartechNonGeneric> 
{ 
    new PartechNonGeneric 
    { 
        Property = false, 
        Data ="One" 
    } 
}; 
data.ForEach(x => x.Data = "PARTECH_" + x.Data);

In this scenario, the prefix data ‘PARTECH_’ gets appended to all the objects that are present in the collection.

Scenario 3

To check whether a particular data is present in the collection, lambda expressions can be used. Consider a scenario where the user wants to check if the first name exists in a collection. In such a scenario lambda expressions can be used.

var data = new List<PartechPersonalData> 
{ 
    new PartechPersonalData
    { 
        FirstName= "Test", 
        LastName="User" 
    } 
}; 
var exists = data.Exists(x => x.FirstName = "PARTECH");

The above code returns true if the data of the selected filter is present else it returns false.

Scenario 4

Consider a list of custom classes and there is a necessity to filter out the object that contains the first name as xx. Post this, do some operations with the specific object rather than the entire list itself (such as the foreach operation which we saw previously).

var data = new List<PartechPersonalData> 
{ 
    new PartechPersonalData
    { 
        FirstName= "Test", 
        LastName="User" 
    }, 
    new PartechPersonalData
    { 
        FirstName= "Test2", 
        LastName="User" 
    } 
}; 
var partechData = data.Find(x => x.FirstName = "Test");

The above code returns the first object that is present in the collection that matches the provided condition as a lambda expression.

Scenario 5

To return multiple objects that match similar conditions, the below code can be used. Imagine a scenario where there is a need to filter students who are 18 years and above. There is a possibility that multiple student records will be present for that condition. With lambda expressions, it is possible to capture all the objects that pass that condition.

var data = new List<PartechPersonalData> 
{ 
    new PartechPersonalData
    { 
        FirstName= "Test", 
        LastName="User", 
        DateOfBirth = "2002-02-21" 
    }, 
    new PartechPersonalData
    { 
        FirstName= "Test2", 
        LastName="User", 
        DateOfBirth = "2002-02-28" 
    } 
}; 
var partechData = data.FindAll(x => (x.DateOfBirth.Year - DateTime.Now.Year) >= 18);

The above code checks through all the records that are present in the custom list and checks for the condition that is being defined and returns all the objects that match the condition provided.

Scenario 6

To return a single property for all the objects that are present in a collection, lambda expressions can be used. Imagine a custom class that holds the first name, last name, and dob. Consider a scenario where there is a necessity to get only the first names that are present in the collection. With lambda expression, it is possible to retrieve only the selected property from the custom class collection.

var data = new List<PartechPersonalData> 
{ 
    new PartechPersonalData
    { 
        FirstName= "Test", 
        LastName="User", 
        DateOfBirth = "2002-02-21" 
    }, 
    new PartechPersonalData
    { 
        FirstName= "Test2", 
        LastName="User", 
        DateOfBirth = "2002-02-28" 
    } 
}; 
var firstNameData = data.Select(x => x.FirstName);

In the above code, the Select statement with the property provides the first name alone from the custom collection.

Similar to the above scenarios, many other operations can be performed with the lambda expressions such as modifying and formatting strings, date format, performing calculations etc.

Conclusion

Lambda expressions are a powerful tool to have. It makes it possible to achieve data manipulation, custom selection, and many other popular operations. The best part is it is done just using simple anonymous methods, lambda operators and input data.

Source: Medium - ParTech

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