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How to check if a string is really empty with C#

Read Time:2 Minute, 17 Second

To be, or not to be (empty), that is the question…

That’s a simple, yet complex, question.

First of all, when a string is not empty? For me, when there is at least one character or one number.

Do it from scratch

Let’s create a custom function to achieve this functionality.

public static bool IsStringEmpty(string myString){ }

Ok, now we have to think of how to check if the string myString is empty.

Of course, the string must be not null. And must not be empty. Maybe… its length must be greater than zero?

public static bool IsStringEmpty(string myString){ return myString==null || myString == String.Empty || myString.Length == 0;
}

Ok, we should be fine. But, what if the string contains only whitespaces?

I mean, the string " ", passed to the IsStringEmpty method, will return true.

If that’s not what we want, we should include this check on the method.
Of course, this implies a bit of complexity to check null values.

public static bool IsStringEmpty(string myString){ return myString==null || myString == String.Empty || myString.Length == 0 || myString.Trim().Length == 0 ;
}

Ok, we covered the most important scenarios.

So we can try the method with our values:

using System;
using System.Collections.Generic; public class Program
{ public static void Main() { var arr = new List() {"1", null, " ", String.Empty, "hello"}; foreach (string txt in arr) { Console.WriteLine("IsStringEmpty? " + IsStringEmpty(txt)); } } public static bool IsStringEmpty(string myString) { if (myString == null) return true; myString = myString.Trim(); return myString == String.Empty || myString.Length == 0; }
}

will return

IsStringEmpty? False
IsStringEmpty? True
IsStringEmpty? True
IsStringEmpty? True
IsStringEmpty? False

Fine. Too tricky, isn’t it? And we just reinvented the wheel.

.NET native methods: String.IsNullOrEmpty and String.IsNullOrWhitespace

C# provides two methods to achieve this result, String.IsNullOrEmpty and  String.IsNullOrWhiteSpace, with a subtle difference.

String.IsNullOrEmpty checks only if the string passed as parameter has at least one symbol, so it doesn’t recognize strings composed by empty characters.

String.IsNullOrWhitespace covers the scenario described in this post. It checks both empty characters and for escape characters.

string str1 = "hello";
Console.WriteLine(String.IsNullOrEmpty(str1)); Console.WriteLine(String.IsNullOrWhiteSpace(str1)); string str2 = null;
Console.WriteLine(String.IsNullOrEmpty(str2)); Console.WriteLine(String.IsNullOrWhiteSpace(str2)); string str3 = "";
Console.WriteLine(String.IsNullOrEmpty(str3)); Console.WriteLine(String.IsNullOrWhiteSpace(str3)); string str4 = "n t ";
Console.WriteLine(String.IsNullOrEmpty(str4)); Console.WriteLine(String.IsNullOrWhiteSpace(str4)); string str5 = " ";
Console.WriteLine(String.IsNullOrEmpty(str5)); Console.WriteLine(String.IsNullOrWhiteSpace(str5)); 

You can see a live example here.

Wrapping up

As you can see, out of the box .NET provides easy methods to handle your strings. You shouldn’t reinvent the wheel when everything is already done.

Source: https://www.code4it.dev/blog/csharp-check-if-string-is-empty

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