I am currently learning C# programming and i am using visual studio 2008.I created two textboxes and a submit button,i want a messagebox to popup telling the user to enter a value in the textbox whenever the submit button is clicked with the texboxes empty.I have tried to solve this but am encontering errors.The two error messages are "cannot implicitly convert type bool to int" and "operator '<' cannot be applied to operands of type int and bool".This is my code,please it might not be well arranged beacause am typing it with my phone.


Private void button1_click(object sender, eventargs e)
{
int answer=10;
bool start=false;
bool end=false;

start=int.tryparse(textbox1.text, out answer);

end=int.tryparse(textbox2.text,out answer);

if (!start)
{
messagebox.show("enter numbers in the textboxes";
}
else
{
for(int i=start; i<end; i++)
{
answer=answer*i;

listbox1.items.add(i+"*"+answer+"="+answer.tostring());
}
}.

Thanks in advance

Though I do Java not C#.The principles are the same.You are trying to convert String values to boolean. I can see that you are trying to read those values and use them as the initial and end values of a for-loop.Check if your textboxes can be constrained to accepting on a set of characters.I use swt(eclipse gui framework) most times in Java,so I normally add a verifylistener to ensure only numbers or any set of characters I want are entered.After that,you have to read the entered numbers as String and parse it to int and use in your for-loop.The error you are getting is trying to convert String to boolean(true or false).They are not the same data type and moreover implicit conversion cannot even take place between Strings and boolean.

If(TextBox1.Text.Lenght == 0)
////
}
Or
If(TextBox1.Text.Equals(""))
{
}

Or
If(TextBox1.Text = String.Empty)
{
}
Any of this should do perferctly

Thanks for the reply,what if i want to limit the textbox characters to only integers,that is i only want integer numbers to be entered in the textbox.How will i do that?

Lakulos: Thanks for the reply,what if i want to limit the textbox characters to only integers,that is i only want integer numbers to be entered in the textbox.How will i do that?

I believe in the property window, there is a sort of input Mask property that you can use or use the Validation rule property.

Like kobojunkie said, one of the properties of the textbox or one of the validation controls gives you what you want. But try:

try{
int val = Convert.ToInt32(TextBox1.Text);
}
Catch(Exception ex)
{
MessageBox.Show("wrong input" ) ;

}

I have tried the codes but none of it is working,i also did not see the input mark and validation rule in the property window.

Sorry bro... The earlier written were for Java. My codes have been modified.

int val = Convert.ToInt32(TextBox1.Text);

Not Integer.Parse which is for java.
The above should work perfectly.

gistme24: Sorry bro... The earlier written were for Java. My codes have been modified.

int val = Convert.ToInt32(TextBox1.Text);

Not Integer.Parse which is for java.
The above should work perfectly.

sory to bother you but am a bit confused,d program is running but say format exception unhandled and it highlighted d "int start=convert.ToInt32(textbox1.text)" in yellow.Also do i still need to use a conditional statement to execute dis program? Pls bear with me,dis is d first programming language am learning

Let's say:
If(TextBox1.Text.Lenght > 0)
{
Try{
Int stat = Convert.ToInt(TextBox1.Text) ;
}
Catch(Exception ex)
{
MessageBox.Show("wrong input" ) ;
}
}
Else
MessageBox.show("Field cannont be blank" ) ;


If ur still having that exception, copy and paste ur codes here let's see.

gistme24: Let's say:
If(TextBox1.Text.Lenght > 0)
{
Try{
Int stat = Convert.ToInt(TextBox1.Text) ;
}
Catch(Exception ex)
{
MessageBox.Show("wrong input" ) ;
}
}
Else
MessageBox.show("Field cannont be blank" ) ;


If ur still having that exception, copy and paste ur codes here let's see.

Its now working,thanks very much,i really appreciate your time.