My Goal: Extracting one value from an Excel Range, and verify for these cells' value to be the same within this range;
When a cell's value is not the same as the other, I need to return null.
Here's a piece of code:
internal object GetValueFromCells(string start, string end, Formats format) {
// Verifying for empty or null parameters here and throwing accordingly...
try {
Range cells = Excel.get_Range(start, end) as Range;
object value = null;
bool sameValue = false;
foreach(Range cell in cells) {
// This condition block shall execute only once, since 'value' shall not be null afterwards.
if (value == null || value == DBNull.Value)
if (Formats.Formated == format) {
value = cell.Text;
// The following results to be false !?...
sameValue = value == cell.Text; // Shall this not be true?
} else {
value = cell.Value2;
// The following results to be false !?...
sameValue = value == cell.Value2; // Shall this not be true?
}
// This results being always false!?...
// Shall this not be true, I wonder?
sameValue = Formats.Formated == format ? value == cell.Text : value == cell.Value2;
if(!sameValue)
return null;
}
return value;
} catch (Exception ex) {
// Exception handling...
}
}
Reading this code, I would humbly expect a value to be returned when all of the cells in the range have the same value (for instance 334).
However, this methods always returns null (Nothing in Visual Basic)!
Anyone might explain what I'm missing here while this:
value == cell.Value2
always returns false?
Perhaps is it my algorithm that isn't quite right?
EDIT #1
This has solved the problem:
sameValue = Formats.Formatted == format ? cell.Text.Equals(value) : cell.Value2.Equals(value);
I accepted #Jerod Houghtelling's answer as his answer suggests both the ToString() and the Equals() methods to solve the problem.
In addition to it, I dislike having to call the ToString() method, since the value can be numbers, and comparing numbers under a string looks odd to me. So I prefer the Equals() way which I adopted within my solution.
I would like to thank #Sir Gallahad and #Jerod Houghtelling for their good answers. This was the first time I had to face such a situation, and they both helped me better understand what was going on under the hood, plus the others who contributed too through comments.
And thanks to those who upvoted my question. This serves a purpose to demonstrate that I was not so dumb asking! =P Hehehe...
I'm guessing that cell.Value2 is returning a new instance of an object each time you call it. Therefore I would deduce the == is checking to see if both sides of the equation are the same instance of the object. To actually compare the value stored on both side you will have to use the .Equals or convert the values to something that can be compared, for example a string.
sameValue = value.Equals( cell.Value2 );
/* or */
sameValue = value.ToString() == cell.Value2.ToString();
Also I don't see value being set in your example.
Probably the value == cell.Value2 are comparing objects that are from different instances.
Try value.ToString() == cell.Value2.ToString()
Related
for some reason I don't seem to be able to put the return in a fashion that captures this stored procedure's return value (0 or -1), either it returns the value which was used to initialize the variable or keeps telling me the local variable is unassigned.
public int changePass(int idUsuario, String old_pass, String new_pass)
{
int result;
try
{
DataTable tablaResultado =
DataBaseAccess.advanceStoredProcedureRequest(
"pa_usuario_change_pass",
new SPP[]
{
new SPP("id_usuario", idUsuario.ToString()),
new SPP("old_pass", old_pass.ToString()),
new SPP("new_pass", new_pass.ToString())
});
if (tablaResultado.Rows.Count > 0)
{
if (tablaResultado.Rows[0] != null)
{
result = (int.Parse(tablaResultado.Rows[0].ItemArray[0].ToString()));
}
}
return result;
}
catch (System.Data.SqlClient.SqlException sqlException)
{
throw sqlException;
}
}
I have multiple methods which follow the same pattern and all of those works, I have been trying to get this to work for awhile now, and I'm sure I'm overlooking something very, very obvious. Either way I cannot find it right now so I was hoping someone could refresh my memory or give me a tip.
The code only assigns a value to the result variable if two different conditions both happen to be true. That is, if the row count is > 0 and the first row is non-null. The compiler is telling you, completely legitimately, that your code contains a path to the return statement where the variable being used hasn't been assigned a value yet.
You need to decide what the method should return if either of those conditions are not true, and then assign that value to the result variable as part of its initialization.
EDIT:
To be clear: it seems you may be overlooking the possibility that your code won't successfully execute the stored procedure. But it can only return a value to be assigned to result when those two conditions are true. You either need to pick a default value that is reasonable to return when one or the other of the conditions aren't true, or you need to fix the code so that those conditions are always both true (and so the SP always executes successfully).
I came across this code:
if (txtUPC.Text.ToString() != null)
...and wonder if this test is even valid - is it possible for the text property to be null? txtUPC is not a dynamically created control. It can be empty, of course, or contain just whitespace, but null? If so, I'd like to know how. Then again, call ToString() on the text property seems like wearing suspenders with a belt, too.
UPDATE
So it seems to me, that for me (remember: .NET 1.1, Windows CE/Compact Framework), this:
if (txtUPC.Text.Trim() != string.Empty)
...is a better test than this:
if (txtUPC.Text.ToString() != null)
However, upon gazing even more intently at this code, it seems that either the outer or the inner gauntlet is redundant/unnecessary, anyway. Note the two shibbeleth-pronunciation-checkers that the method includes:
if (txtUPC.Text.ToString() != null)
{
if (txtUPC.Text.Length > 0)
{
. . .
else
{
MessageBox.Show("Please enter a value in the item field");
txtUPC.Focus();
}
}
else
{
MessageBox.Show("Please enter a value in the item field");
txtUPC.Focus();
}
. . .
It would seem one gatekeeper/gauntleteer would be enough - either checking this way:
if (txtUPC.Text.Trim() != string.Empty)
...or this way:
if (txtUPC.Text.Trim().Length > 0)
a?
I don't think it could ever be null (perhaps there is a difference between a winforms/asp.net/wpf textbox, but I don't think so). Although a better check would be:
if (String.IsNullOrEmpty(txtUPC.Text) { ... }
Or, depending on your requirements:
if (String.IsNullOrWhiteSpace(txtUPC.Text) { ... }
And yes, the .ToString() is not needed.
The problem I see with that code is that .ToString() returns the object as a String. If in this case, the object is a String it just returns the original string (exactly as is)
Problem is if .Text is null, then the method call of .ToString() would throw a NullReferenceException.
You can see more on the .ToString override here
See this code for an example:
String str1 = "";
String str2 = null;
Console.WriteLine("Original str1: {0}", str1);
Console.WriteLine("Original str2: {0}", str2);
Console.WriteLine("ToString str1: {0}", str1.ToString());
Console.WriteLine("ToString str2: {0}", str2.ToString());
Will throw the exception on the ToString str2 line
I'm trying to make a simple parallel.For and It seems to be getting the same "i" over and over again.
My code is:
String[] str = new String[10000];
Parallel.For(0,10000, i=>
{
if(str[i] == string.Empty)
str[i] = "ok";
else
str[i] = "SameValue";
});
I would expect it to never get to "else"
string.Empty does not equal null, change your if condition to
if (String.IsNullOrEmpty(str[i]))
I would expect it to never get to "else"
Wrong - the string array elements are initialized with null (their default value as reference type) - not string.Empty. Hence only the else part is ever executed.
You can easily verify this yourself by setting a break point on the if statement.
Take a look at this code:
System.Web.SessionState.HttpSessionState ss = HttpContext.Current.Session["pdfDocument"] ?? false;
if ((Boolean)ss)
{
Label1.Text = (String)Session["docName"];
}
Basically I want to check if HttpContext.Current.Session["pdfDocument"] is not null, and if it isn't to cast to Boolean, then check if its true or false.
I'm trying to avoid nested if statements and figured there would be a more elegant way to do it. I'm therefore only interested in answers that contain the conditional ? operator.
Any tips?
Why do you use ss variable?
What about this:
if (HttpContext.Current.Session["pdfDocument"] != null)
{
Label1.Text = (String)Session["docName"];
}
object ss = HttpContext.Current.Session["pdfDocument"] ?? false;
if ((Boolean)ss)
{
Label1.Text = (String)Session["docName"];
}
Not sure exactly what you're asking for, how about:
System.Web.SessionState.HttpSessionState ss;
Label1.Text = (Boolean)((ss = HttpContext.Current.Session["pdfDocument"]) ?? false) ? (String)Session["docName"] : Label1.Text;
Should leave ss with either a valid session or null, avoids the problem of trying to store false to ss and completely skips the subsequent 'if'. Though there's a repetition of Label1.Text.
Note: this has been edited to take account of the comment by Dave below.
The problem is that you can't do this:
SessionState.HttpSessionState ss = false;
Try putting your nested ifs into an extension method then call that instead.
HttpContext.Current.Session is an System.Web.SessionState.HttpSessionState object, which is a hash or dictionary, as some may call it, of different objects, so unless you're storing an HttpSessionState object as the "pdfDocument" location the first line is incorrect.
If you're actually storing a bool in the "pdfDocument" location which may or may not already be in this slot, you could cast that directly to a bool and null coalesce it: var ss = (bool)(HttpContext.Current.Session["pdfDocument"] ?? false);.
If you're possibly storing some other kind of object in the "pdfDocument" location you could just see if it's currently at that location by checking for null: var ss = HttpContext.Current.Session["pdfDocument"] != null;.
You can try this, though I don't know if it fits your aesthetics:
bool isPdfDocumentSet =
bool.TryParse((HttpContext.Current.Session["pdfDocument"] as string,
out isPdfDocumentSet)
? isPdfDocumentSet
: false;
EDIT: There is actually an even more concise way of doing it:
bool isPdfDocumentSet =
bool.TryParse(HttpContext.Current.Session["pdfDocument"] as string,
out isPdfDocumentSet) && isPdfDocumentSet;
I think the closest you will get to the solution taking that path is following:
System.Web.SessionState.HttpSessionState ss = HttpContext.Current.Session["pdfDocument"];
if (ss != null)
{
Label1.Text = (String)Session["docName"];
}
In my attempt at dissecting a bit of C# I am afraid I do not understand either the goal or the logic of this bit of code:
if (!string.IsNullOrEmpty(str2) && (Strings.UCase(Strings.Left(str2, 1)) != Strings.Left(str2, 1)))
{
return false;
}
I understand the first part is checking if str2 is "not null", however the second part is coming off a bit flaky. So we UCase the first character of str2, and if it does not equal the first character of str2 (which is NOT "UCase"d), then return "false"?
Maybe I am not missing anything and what I described above is in fact what the code is doing. If this is the case, can we reform this into something else that offers the same result,say for example, check if str2 is uppercase or not? I feel like this is the end goal.
You thoughts?
Yes, you understood the code right.
It looks like something translated from VB using a translation tool, as it's using functions from the VisualBasic namespace. I would rather write it with String methods:
if (!String.IsNullOrEmpty(str2) && str2.Substring(0,1).ToUpper() != str2.SubString(0,1)) {
return false;
}
Or simply getting the first character as a character instead of as a string, and use the IsLower method of the Char class:
if (!string.IsNullOrEmpty(str2) && Char.IsLower(str2[0])) {
return false;
}
My bet is that they are really just testing whether the first character is uppercase. The initial "IsNullOrEmpty" test is just there to make sure that the real test doesn't throw an exception.
The big question: if there is no string value (null or empty) this will not return false. Is that the expected outcome?
Code Objective in English :)
If the non-empty string begins with a lower case character then return false
This is the same, but refactored:
if (!string.IsNullOrEmpty(str2)) {
string s = Strings.Left(str2, 1);
if (Strings.UCase(s) != s) {
return false;
}
}
It is clear that this code tests that the first letter of str2 is or isn't in uppercase when it has any character.
I share the perceptions you have when you say : "I do not understand either the goal or the logic of this bit of code" :) A test that returns only 'false is "fishy" : presumably "something" is waiting for a boolean to be returned, and nothing is returned if the result of this evaluates to 'true.
But if I had to write such a function I'd use the alternative OR logic :
return (! (String.IsNullOrEmpty(testString) || testString.ToUpper()[0] == testString[0]));