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In my first three articles about Visual C# Express, I wrote in fairly general terms about how to build modern C# programs, using the example of the InterestCalculator program. In this article I would like to talk about

According to USFDA, a combination product is one composed of any combination of a drug and device; biological product and device; drug and biological product

the very specific problem of converting user input from textual information to numeric information.

TextBox Accepts only Strings

There are four user input text boxes in the CompoundGrowth form of the I

; or drug, device, and biological product and fixed dose combination would include two or more combinations of drug.

Examples of combination products may in

nterestCalculator program, and all of them APPEAR to accept numeric; but in fact they do not. They all accept strings, for one simple reason. Strings are the only data accepted by the .net TextBox control. In fact th

lude drug-coated devices, drugs packaged with delivery devices in medical kits, and drugs and devices packaged separately but intended to be used together.

e only way to read the contents of the TextBox control is via the "Text" property, which returns a string.

Parse Function to the Rescue

Since the Textbox control accepts only strings, the programmer is s

here is enormous increase in the number of combination products entering the market in the recent years. Combination products have proven advantages but fixe

tuck with the problem of converting from a C# string type to a C# numeric type. There are in fact several methods for doing this using the .net class library, but in this article I will show you how to do it using the

d dose combinations are still in the process of convincing regulatory authority on their advantages over the single ingredient formulations.

Combination pro

arse function.

Nearly every numeric data type has a Parse function which operates on a string and converts it to a numeric data type. For example, the code to convert from a string to a double would look something lik

ucts have become life saving products for the pharmaceutical companies who doesn’t have many innovative molecules in their product pipeline and have been inc

e the following:

// Convert string in txtPrincipal TextBox to a double precision number mPrincipal= Double.Parse( txtPrincipal.Text);

That's all there is to it . . . except for one small

easingly used in the product life cycle management. Even the companies having product patents are trying to extend their product life cycle through the combi

problem. What happens when if someone types something like "1A3Y" into the txtPrincipal TextBox? Now we have a problem.

Recovering from Erroneous Inputs

It would easy to design forms if people always

nation products and maximize the revenues. But the companies involved in this practice are overlooking that they are burdening the patients both economically

hit the right buttons and always entered the correct data. The challenge of designing and coding forms is to give them reasonable error recovery scenarios.

The .net class library supports a solution to the problem det

and physically. They need to rightly judge the benefits of the combination products and they have to even look at the risks involved when combining the produ

ecting and handling erroneous input. In addition to the Parse function there is a TryParse function associated with each numeric data type. The TryParse function does just what you would think, it tries to parse a tex

ts. Some of the combination products were well accepted by physicians while others suffered. Companies involved in development of combination products are fi

string and returns boolean true if it is able to and boolean false if it cannot.

Now the code, contained in the function ValidateInput looks more like this:

if (!double.TryParse(txtPrincipal.Text, out mPrincip

ding difficulty in defining their combination products and facing various challenges from selecting a combination to marketing it.

Following aspects would a

al))
{

txtAmount.AppendText("Principal must be a number");
success = false;

}

The same type test is repeated for each of the numeric text boxes in the form, and the function

dd to the challenges in developing combination products:

Which markets to tap where the combination products can do fairly well?
Which combination prod

ValidateInput returns false if any of the tests fail.

In addition, as you can see above (or in your copy of downloaded code), an error message is printed to the user for each text box which does not validate proper

cts are meaningful and rational?
Which therapeutic categories to select?
Which Combinations can address unmet needs of the patients?
Do combin

ly; and the compounded investment value will not be displayed unless all four text box inputs validate.

If an error message is displayed, the user has the option of correcting the contents of the invalid TextBox(es) an

tions increase the patient compliance?
What would be the developing cost?
How to tackle the risks encountered during combination product developmen

d resubmitting by pushing the "Calculate Amount" button again.

Other Options

Although this article did not discuss them, I would like to briefly mention two other options for doing the string to numeric

t?

As combination products don't fit into the traditional categories of drugs, medical devices, or biological products, the USFDA is in the process of devel

onversion.

(1) Build the conversion into the TextBox, by inheriting the TextBox class and adding a text-to-numeric conversion property or method. That is a very elegant solution and would make a lot of sense i

ping new procedures for reviewing their safety, efficacy and quality.

Professional from academic institutions, pharmaceutical industries, health care indust

f you were using a lot of numeric input text boxes.

(2) The Convert class contains methods to convert every base type to every other base type. The methods Convert.ToDouble and Convert.ToUInt64 could be used in

y and representatives from various regulatory agencies are working out to design the regulatory requirements for manufacture and sale of combination products

stead of double.TryParse and ulong.TryParse respectively; however these methods do not return the status of the conversion so the programmer would need to implement exception code to trap invalid input.

Summary
.

As there is an increasing trend of the combination products companies manufacturing such products should be able to tackle the problems involved in the de
b>

You can find a copy of the Interest Calculator Code on my Article Support Page.

The .net TextBox class allows only textual input, so the programmer need
elopment. They need to be wiser in analyzing the market trends and the regulatory requirements.

Companies that provide selfless information through particip
s a way to convert the string value of the TextBox to a numeric value. The TryParse function solves this problem with the additional bonus that it performs error checking and returns the boolean status of the conversion

tion in industry events and feedback to regulatory authorities would be able to face the challenges and will be successful in developing combination products

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Wiki Articles - Visual C# Express - Parsing User Input (4th In A Series)

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