.NET (Core and Framework)

class MyForm : Form
{
   ...
   Label[] labelList;  // Array holding the labels to modify
   const int NumLabels = 5;  // Number of labels in the array
   ...

   // Constructor for your form
   public MyForm()
   {
     ...
     // create and fill the label array - just using five in this example
     labelList = new Label[] { label1, label2, label3, label4, label5 };
     ...
   }

   public void DoSomethingWithLabels()
   {
     // loop through the array of labels
     for( int i=0; i<NumLabels; i++ )
     {
       // change the caption on this label
       labelList[i].Text = "Hello World!";
     }
   }
}

foreach (Control myControl in System.Forms.Controls)
{
}