C# For loop and arrays

Question

I need help with this loop and displaying the array correctly into a label. Here is the Code

private void ErrorEquipment()
{
    string[] Equips = { "Projector", "Computer", "Network", "Webcam" };

    for (int i = 0; i <= 3; i++)
    {
        if (venue.Equipment[i] == true)
        {
            lblEquipment.Text = ("Room Has " + Equips[i]);
        }
    }
}

What I want is to check if the venue has the equipment and if so it, display what equipment the venue has in a label. Currently it checks that but if a venue has more than one equipment available and it overwrites the first equipment that was put in the label.

Do you want to concat all equipments in the same label?

Yuval Itzchakov
– Yuval Itzchakov

2015-01-25 14:55:36 +00:00
Commented Jan 25, 2015 at 14:55 — Yuval Itzchakov
– Yuval Itzchakov, Commented Jan 25, 2015 at 14:55

Ludovic Feltz · Accepted Answer · 2015-01-25 14:52:17Z

2

That's because you redefine your variable lblEquipment.Text in every iteration. Try this instead:

    lblEquipment.Text = "Room Has ";
    for (int i = 0; i <= 3; i++)
    {
        if (venue.Equipment[i] == true)
        {
            lblEquipment.Text += Equips[i] + " ";
        }
    }

answered Jan 25, 2015 at 14:52

Ludovic Feltz

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Comments

DevEstacion · Accepted Answer · 2015-01-25 15:05:17Z

You can do it something like this.

lblEquipment.Text = "Room Has ";
for (int counter = 0; counter <= 3; counter++)
{
    if (venue.Equipment[counter] == true)
        lblEquipment.Text += Equips[counter] + " ";
}

But this is too inefficient because when you concatenate strings, it always creates a new instance of string because string is immutable, and since you're in a for loop, the instance you're creating is being wasted.

To better implement this, you must create a StringBuilder object and then ToString it after the loop. Something like this.

StringBuilder builder = new StringBuilder();
builder.Append("Room Has ");
for (int counter = 0; counter <= 3; counter++)
{
    if (venue.Equipment[counter] == true)
        builder.Append(Equips[counter] + " ");
}
lblEquipment.Text = builder.ToString();

More info about Immutable objects here: C# Tips & Tricks: Immutable Types

Ehsan Sajjad · Accepted Answer · 2015-01-25 15:28:51Z

1

you are replacing each time Label lblEquipment value.

you need to do String Concatenation instead of just assigning new value.

Use a variable to Store result and then display:

 string rooms ="Room Has ";
 for (int i = 0; i <= 3; i++) 
{ 
  if (venue.Equipment[i] == true) 
     rooms += ","+Equips[i]; // concatenating with previous value
}
lblEquipment.Text = rooms;

A linq inspired solution would be:

var result = venue.Equipment.Select((v, index) => new { v, index })
                            .Where(pair => pair.v == true && pair.index <=3)
                            .Select(pair => Equips[pair.index]);

lblEquipment.Text = "Room Has "+ string.Join(",",result);

edited Jan 25, 2015 at 15:28

answered Jan 25, 2015 at 14:57

Ehsan Sajjad

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