how to resolve error getting in if condition

Question

1.67/5 (3 votes)

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pls check the coding
of if condition
and tell the error

C#

private void OK_Click(object sender, EventArgs e)
       {
            if(UsernameTextBox.Text ="Manager" & PasswordTextBox.Text = "Maintenance")
           {
           frmMDI m=new frmMDI();
           m.Show();
           }
            else
           MessageBox.Show("Unauthorised User", "Authentication");
           UsernameTextBox.Focus();
           UsernameTextBox.SelectionStart = 0;
       }

thanx in advance
regards

Posted 17-May-11 1:39am

shivani 2013

Add a Solution

4 solutions

Solution 2

You are using the assignment = instead of comparison ==

if(UsernameTextBox.Text == "Manager" & PasswordTextBox.Text == "Maintenance")

Posted 17-May-11 1:47am

Jeremy Hutchinson

Comments

Kim Togo 17-May-11 10:32am

Almost correct. The bit operator & has to be change to &&

Jeremy Hutchinson 17-May-11 11:14am

While I generally agree it is good practice to use && over & where appropriate (there's places where it's not), it is certainly not required. In a case like this were you are just comparing strings it is not going to have any noticeable effect on performance and amounts to a style issue.

If I were going to correct a style issue, the first thing I would change is to put braces around the else code to make it clear that the Focus and selection setting happen for both paths, which may or may not be what was intended.

Kim Togo 17-May-11 13:03pm

I just prefer to use "&&" operator, it only evaluate second expression it the first is true.
Then I can write code like

if (this.Name != null && this.Name.Contains("Hello"))
{
}

But you are right, there is no performance degree in this code :-)

Sergey Alexandrovich Kryukov 17-May-11 18:48pm

Many thins are technically not required, but absolutely required to make a good call.
Wrong excuse.
--SA

Solution 4

This line is wrong:

C#

if(UsernameTextBox.Text ="Manager" & PasswordTextBox.Text = "Maintenance")

It should read:

C#

if(UsernameTextBox.Text == "Manager" & PasswordTextBox.Text == "Maintenance")

In C# you use = operator to assign and == to compare.

Posted 17-May-11 1:49am

Fabio V Silva

Comments

Kim Togo 17-May-11 10:30am

Almost correct. The bit operator & has to be change to &&

Fabio V Silva 17-May-11 10:35am

Why?

Kim Togo 17-May-11 13:02pm

Sorry. Of cause you can do it like that. :-)
Using one "&" operator just evaluates all expressions.

I just prefer to use "&&" operator, it only evaluate second expression it the first is true.
Then I can write code like

if (this.Name != null && this.Name.Contains("Hello"))
{
}

Sergey Alexandrovich Kryukov 17-May-11 18:49pm

Because. Kim is absolutely right. It's a mistake, even though it would work the same way.
--SA

Fabio V Silva 18-May-11 14:57pm

"Because"?! That's a good answer...

Sergey Alexandrovich Kryukov 18-May-11 18:01pm

Disagree, sorry. It's only "almost good". Must be "&&", even though it's functionally equivalent in this case. "&" is only needed when ANDing predicate with side effect, in order not avoid "optimizing out" of this side effect. Is it clear?
--SA

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Ankur^\m/ · Accepted Answer · 2011-05-17T01:48:00

Solution 3

Change his line:

C#

if(UsernameTextBox.Text ="Manager" & PasswordTextBox.Text = "Maintenance")

to

C#

if(UsernameTextBox.Text == "Manager" && PasswordTextBox.Text == "Maintenance")

Posted 17-May-11 1:48am

Ankur^\m/

Updated 17-May-11 1:50am

v2

Comments

Kim Togo 17-May-11 10:33am

Correct my 5 :-)

Ankur^\m/ 18-May-11 0:35am

Thanks, Kim!

Sergey Alexandrovich Kryukov 17-May-11 18:46pm

Agree, 5.
--SA

Ankur^\m/ 18-May-11 0:36am

Thanks, SA!

VysakhMenon · Accepted Answer · 2011-05-17T01:45:00

Solution 1

C#

private void OK_Click(object sender, EventArgs e)
       {
            if(UsernameTextBox.Text =="Manager" && PasswordTextBox.Text == "Maintenance")
           {
           frmMDI m=new frmMDI();
           m.Show();
           }
            else
           MessageBox.Show("Unauthorised User", "Authentication");
           UsernameTextBox.Focus();
           UsernameTextBox.SelectionStart = 0;
       }

Posted 17-May-11 1:45am

VysakhMenon

Updated 17-May-11 1:49am

v2

Comments

Kim Togo 17-May-11 10:32am

Correct, my 5

Sergey Alexandrovich Kryukov 17-May-11 18:47pm

Agree, 5.
--SA

jsc42 25-May-11 12:56pm

Many style gurus suggest comparing strings against variables, instead of comparing variables against strings just so that compilers would catch the mistaken use of '=' instead of '=='. Viz:

if ("Manager" == UsernameTextBox.Text && "Maintenance" == PasswordTextBox.Text)

which is valid whereas

if ("Manager" = UsernameTextBox.Text && "Maintenance" = PasswordTextBox.Text)

is invalid.

Personnaly, I think it looks clunky and awkward. Anyone who uses that construct is already aware of the issue of confusing '==' and '=', and hence probably does not need this backward construct. Conversely, people who are likely to fall foul of '=' instead of '==' are unlikely to be ones who would use the backwards construct. But I am sure there must be a set of people somewhere that would benefit fropm this backwards construct.