C# Linq FirstorDefault Method

Use the FirstorDefault() method to return the first element of a sequence or a default value if element isn’t there.

The following is our empty list −

List<double> val = new List<double> { };

Now, we cannot display the first element, since it is an empty collection. For that, use the FirstorDefault() method to display the default value.

val.AsQueryable().FirstOrDefault();

The following is the complete example.

Example

using System;
using System.Collections.Generic;
using System.Linq;
class Demo {
   static void Main() {
      List<double> val = new List<double> { };
      double d = val.AsQueryable().FirstOrDefault();
      Console.WriteLine("Default Value = "+d);
      if (d == 0.0D) {
         d = 0.1D;
      }
      Console.WriteLine("Default Value changed = "+d);
   }
}

Output

Default Value = 0
Default Value changed = 0.1