Develop Reference

How to get around with this conversion issue?

I created a GUI which inputs a value number into another program and stores them in tags. I have a weird conversion problem. When I input 8.5 I get back a string 8.500000000000000... so I use the TryParse and the Double.ToString() method to get around this issue. But the bizarre part is that when I try with 6.9 the string becomes 6.9000000005367431600000.I use 2 dll which might be the cause of this problem. I've read this Decimals explanation but I don't understand how this can be fix my problem. How to get around with this conversion issue?
My Conversion method
private bool TryWrite()
{
// Read() returns a string(which represents int,double, float or string) read from another application
string Oldcopy = _inTouchWrapper.Read(tagNameBox.Text);
// Write() Write my input number into the application stored in a specific tag
_inTouchWrapper.Write(tagNameBox.Text, ValueBox.Text);
//OldCopy is to input back the old copy is the Write (new copy) cannot be performed
string newCopy = _inTouchWrapper.Read(tagNameBox.Text);
if (ValueBox.Text == Double.Parse(newCopy).ToString())
{
return true;
}
else
{
_inTouchWrapper.Write(tagNameBox.Text, Oldcopy);
return false;
}
}
More explanation about the software/and my code. The software has tags ex: Alarm1, TimeString...
Each tag has a type (int, real(a float), string) and a value. This value depends on the type. I cannot input 5.6 if the tag type is int. So I created this method which verifies is the input value can indeed be added in the software. How it works: I input a value in the software, read it back and if the added value matches with the read value, I indeed input it. Else, I input back the oldCopy.

It seems that string "6.9" is not directly converted to double. If is first converted to float and then casted to double. Here is an example:
var f = float.Parse("6.9");
var d = (double)f;
System.Diagnostics.Debug.WriteLine(d.ToString()); //6.90000009536743
PS: Why you not have the same issue with '8.5' is that it can exactly be represented in binary form.

How to pass decimal value from textbox to parameter

I am trying to create a save Button and it includes 2 values in TextBox controls that are considered currency in sql. They are decimal in the TextBox. How do I pass the value? I tried this to no avail:
decimal taxOpen = Convert.ToDecimal(taxOpenTextBox).Text;
Any help on the correct syntax would be great.

You need to access the Text property. You also should use TryParse, which returns false instead of throwing an exception if the parse fails:
decimal value;
if(!decimal.TryParse(taxOpenTextBox.Text,
NumberStyles.Currency,
NumberFormatInfo.InvariantInfo,
out value))
MessageBox.Show("Please enter a valid number");
The needed things are found in System.Globalization.

You need to get the value of the taxOpenTextBox, not the box itself.

Alternative for Microsoft.VisualBasic.Information.IsNumeric in C#

attrval[5] = WrmService.WindowsAgent.AgentVersion;
From above if attrval[5] is null or not getting any value or any strings other than numeric values I want to assign attrval[5] to value '0.0.0.0' otherwise I will
display the numeric value which is coming.What coding i have to implement here
as per the information while doing googling I did this
attrval[5] = (WrmService.WindowsAgent.AgentVersion == null || Microsoft.VisualBasic.Information.IsNumeric(WrmService.WindowsAgent.AgentVersion)) ?
"0.0.0.0" : WrmService.WindowsAgent.AgentVersion;
but Microsoft.VisualBasic.Information.IsNumeric making problems. Is there any similar one in C#?
only two outputs I required one will be numeric and one will be any other, it can be string or null whatever it i have to set in to 0.0.0.0

Try
if(!int.TryParse(WrmService.WindowsAgent.AgentVersion, out attrval[5])) attrval[5] = 0;
In this case, if AgentVersion is numeric, it will place the parsed value into attrval[5], otherwise it will set it to 0.
edit
Ah I guess you are looking for:
attrval[5] = string.IsNullOrEmpty(WrmService.WindowsAgent.AgentVersion) ? "0.0.0.0" : WrmService.WindowsAgent.AgentVersion;

I would recomend using something like
Int32.TryParse Method (String, Int32)
See also C# Equivalent of VB's IsNumeric()

You could use Int32.TryParse() to check if it is an integer value.

Parsing a decimal from a DataReader

I found a workaround for this error, but am now really curious as to why this would be happening, was wondering if anyone else has had this error.
My function is as follows:
public void Blog_GetRating(int blogID, ref decimal rating, ref int voteCount)
{
// Sql statements
// Sql commands
if (DataReader.Read())
{
// this line throws a 'Input string was not in a correct format.' error.
rating = decimal.Parse(DataReader["Rating"].ToString());
// this works absolutly fine?!
decimal _rating = 0;
decimal.TryParse(DataReader["Rating"].ToString(), out _rating);
rating = _rating;
}
}
Anyone ever seen that before?
What's even weirder is if i type this:
rating = decimal.Parse("4.0");
that works fine, the 4.0 is what is coming out from my DataReader.
As I said previous, the TryParse method works fine so it's not stopping me from carrying, but now I'm really interested to see if anyone has an answer for it.
Looking forward to some replies!
Sean
EDIT - SOLVED
The decimal.Parse method was working fine, the second time the function was running (was in a loop), a post hadn't been rated so a null value was being returned by the data reader. Wrapping COALESCE round my calculation in SQL solved the problem fine. Hence why, as you said, the tryparse method wasn't throwing an exception, just keeping the default of 0 to _rating.

That doesn't look weird to me at all.
Decimal.Parse() is supposed to throw an exception for bad formats. Decimal.TryParse() will not throw that exception, but instead just return false. The kicker is that you're not checking the return value from Decimal.TryParse(). I'll give you real good odds that Decimal.TryParse() returns false for every input that causes an exception with Decimal.Parse(), and true everywhere else. And when Decimal.TryParse() returns false, the output argument is always just "0".
The one possible caveat is localization. If Decimal.Parse() is complaining about a seemingly normal input, you might check if the number format (current culture) used on your server uses a comma rather than a decimal to separate the coefficient from the mantissa. But given your "4.0" test worked fine, I doubt this is the problem.
Finally, when doing this conversion from data reader you should consider the source column type of the data reader. If might already be a decimal. Why convert it to a string only to convert it back?

You are saying this:
// this works absolutly fine?!
decimal _rating = 0;
decimal.TryParse(DataReader["Rating"].ToString(), out _rating);
But you didn't actually check the return value of TryParse. I would guess that your TryParse is actually failing (returning false), since decimal.Parse and decimal.TryParse use the same "rules" for parsing, given the overloads you're using.
I suspect that neither is working as you think. Both are probably failing, but TryParse won't throw.

The sql decimal column won't parse to a string that can convert to a Decimal, so tryparse will return false. Try something like this:
if (Convert.IsDBNull(reader["DecimalColumn"]))
{
decimalData = 0m;
}
else
{
decimalData = reader.GetDecimal(reader.GetOrdinal("DecimalColumn"));
}

I am facing same problem today.
Try this:
rating = decimal.Parse("4,0");
It will give you same error.
The reason behind this is the culture. In the French culture, 4.0 is represented as 4,0, and hence it throws an Exception.
decimal.TryParse is culture invariant method and hence it works fine you.

Change your TryParse to this and try again:
if (!decimal.TryParse(DataReader["Rating"].ToString(), out _rating))
{
throw new Exception("Input string was not in a correct format");
}
I bet this does throw...

C# Why won't this substring work? Error: Input string was not in a correct format

The problem is with the convert of the txt box value, but why?
string strChar = strTest.Substring(0, Convert.ToInt16(txtBoxValue.Text));
Error is: Input string was not in a correct format.
Thanks all.

txtBoxValue.Text probably does not contain a valid int16.

A good way to avoid that error is to use .tryParse (.net 2.0 and up)
int subLength;
if(!int.TryParse(txtBoxValue.Text,out subLength)
subLength= 0;
string strChar = strTest.Substring(0, subLength);
This way, if txtBoxValue.Textdoes not contain a valid number then subLength will be set to 0;

One thing you may want to try is using TryParse
Int16 myInt16;
if(Int16.TryParse(myString, out myInt16)
{
string strChar = strTest.Substring(0, myInt16);
}
else
{
MessageBox.Show("Hey this isn't an Int16!");
}

A couple reasons the code could be faulty.
To really nail it down, put your short conversion on a new line, like this:
short val = Convert.ToInt16(txtBoxValue.Text);
string strChar = strTest.Substring(0, val);
Likely the value in txtBoxValue.Text is not a short (it might be too big, or have alpha characters in it). If it is valid and val gets assigned, then strTest might not have enough characters in it for substring to work, although this normally returns a different error. Also, the second parameter of substring might require an int (not sure, can't test right now) so you may need to actually convert to int32 instead of 16.
What is the value of txtBoxValue.Text during your tests?

ASP.NET offers several validation controls for checking user input. You should use something like a CompareValidator or RegularExpressionValiditor in your WebForm if you're expecting a specific type of input, eg, an Integer.