How to handle Thread in c# ?

Nafihudheen KT

14y7.8kC#

Hai,

I want to do the printing from my dot net project as background work as a thread, for that what I did is, first collect the each output string to a collection of string

like this
myOutputStringCollection.Add(str);

then after collecting all lines I want to send it to printer, I write code like this which executes a thread

public static void printAllLines()
{
Thread t = new Thread(sendToPrinter);
t.Start();//starts the thread
}

and the send to printer function is like this

public static void sendToPrinter()
{
int count = myOutputStringCollection.Count;
string[] myArray = new string[count];
myOutputStringCollection.CopyTo(myArray, 0);
for (int i = 0; i < count; i++)
{
SendStringToPrinter(myArray[i].ToString());
}
Array.Clear(myArray, 0, myArray.Length);
}

but the problem here am facing is, if I click the print button more than one times Immediately then the printing alignment is not correct, I think if I handle the thread execution properly then it will be all right, If any body know more about threading and its operation then pls share here

Thanks in advance.

6 Replies

Know the answer? Post it — somebody with the same question will find it here.

Vulpes14y ago
Accepted answer
To prevent this problem from occurring, I'd disable the print button just before you start the thread and then re-enable it after the strings have been sent to the printer:

public static void printAllLines()
{
btnPrint.Enabled = false;
Thread t = new Thread(sendToPrinter);
t.Start();//starts the thread
}

public static void sendToPrinter()
{
int count = myOutputStringCollection.Count;
string[] myArray = new string[count];
myOutputStringCollection.CopyTo(myArray, 0);
for (int i = 0; i < count; i++)
{
SendStringToPrinter(myArray[i]); // no need for ToString() as it's already a string
}

// re-enable print button by marshalling to UI thread
this.Invoke(new MethodInvoker(delegate()
{
btnPrint.Enabled = true;
}));
}

The call to Array.Clear() shouldn't be needed as myArray is a local variable and will therefore be destroyed anyway when the sendToPrinter method (and the thread) ends.
Nafihudheen KT14y ago
Thanks very much, your code works perfect.
Vulpes14y ago
Sorry, I forgot to change the first line of that. It should be:

Form1.Me.Invoke(new MethodInvoker(delegate()
{
Form1.Me.btnPrint.Enabled = true;
}));
Nafihudheen KT14y ago
Thanks again Vulpes, its really help me but I can not code this

this.Invoke(new MethodInvoker(delegate()
{
Form1.Me.btnPrint.Enabled = true;
}));

'this.Invoke' can not create in my class file, what is the solution any suggesion
Vulpes14y ago
Suppose btnPrint is on Form1:

1. In the Properties Box for btnPrint change its Modifiers property from private to internal.

2. Add the highlighted code to Form1:

public partial class Form1 : Form
{
internal static Form1 Me;

public Form1()
{
InitializeComponent();
Me = this;
}

// rest of form code
}

3. Change your methods as follows:

public static void printAllLines()
{
Form1.Me.btnPrint.Enabled = false;
Thread t = new Thread(sendToPrinter);
t.Start();//starts the thread
}

public static void sendToPrinter()
{
int count = myOutputStringCollection.Count;
string[] myArray = new string[count];
myOutputStringCollection.CopyTo(myArray, 0);
for (int i = 0; i < count; i++)
{
SendStringToPrinter(myArray[i]); // no need for ToString() as it's already a string
}

// re-enable print button by marshalling to UI thread
this.Invoke(new MethodInvoker(delegate()
{
Form1.Me.btnPrint.Enabled = true;
}));
}

4. If the name of the form is not Form1, then replace it with the actual name throughout the above code.
Nafihudheen KT14y ago
Thank you for your replay Vulpes, I think this is a correct solution but I write the functions printAllLines(), sendToPrinter() in separate a class file, not in the form where print button placed, then how can I code this pls help me..