CODEWITHSUNDEEP
c#event-handling
zurfyx
zurfyx

Reputation: 32767

C# EventHandler with parameters changing its value

I have a table which keeps growing its size as the user inputs them, and each row has a 'X' Label to remove them as well.

table.RowCount is always up-to-date and so I have a function ~like following that is executed everytime I create a new row:

private void storeValues(){
    Label removeLabel = new Label(); 
    removeLabel.Text = "✗";
    removLabel.Click += new EventHandler((s, e) => removeLabel_Click(s, e, table.RowCount));
}

The thing is that all removeLabel's always call the click event with the same parameter value which is the table.RowCount NOT the one I created them with but the value is currently having, so I'm always getting the last row deleted.

private void removeLabel_Click(object sender, EventArgs e, int index){
    removeFromTable(index);
}

How can I save a fixed value to each removeLabel?

Upvotes: 0

Views: 114

Answers (2)

Marc Gravell
Marc Gravell

Reputation: 1062855

Yes; that is what happens with lexical closures. The only thing you are actually capturing here is the implicit this - the value of the expression this.table.RowCount is evaluated at the time the delegate is invoked, every time the delegate is invoked.

If you want to capture a snapshot: capture a snapshot

var count = table.RowCount;
removLabel.Click += new EventHandler((s, e) => removeLabel_Click(s, e, count));

Upvotes: 2

paul
paul

Reputation: 22001

removeLabel.Tag = table.RowCount;

then get the Tag value in the event handler

Upvotes: 0

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