ASP.NET 3.5: A Beginner's Guide - www.mustafaof.com

54ASP.NET 3.5: A Beginner’s GuideThe rest of the method converts data entered as string to real numbers to be used in thecalculations. For example, the C# lines1 = Convert.ToDouble(ScoreA.Text) * .85;takes whatever was entered into the TextBox in the ASP.NET portion of the classinto a number (a double) and assigns the value to the variable s1. Included is themultiplication of the text from ASP.NET that has to be converted to a floating-pointnumber (the double type in this case) by .85. The TextBox field with the referencename (ID) of ScoreA originated in the linein ASP.NET.Going in the opposite direction, to output the results of the multiplication and additionto the Total Label field, the numeric values have to be re-converted to text as thefollowing C# line shows:Total.Text = Convert.ToString(s1 + s2);So, in the same way that the Convert class uses the ToDouble method to convertfrom a string to a number, ToString converts back to a string that can be used in aLabel output form. Think of it as a roundtrip beginning with the ASP.NET structures andthe C# engine kick-starting the user events or events from some other state in the program.Basic C# StructuresIn this section, we’re going to look at the basic C# structures independent of ASP.NET. Thenin the examples, you will see how these structures are used in conjunction with ASP.NET ina partial class. However, for the time being this section focuses on the C# structures.Variables and ConstantsAs implied in the previous sections in this chapter, a variable is a container-like structureused to store data. The data in the container can change in value—it varies; hence, theterm variable. As you saw in the previous discussion, you need to provide variables witha type, and you cannot pass the value of one variable type to a variable of a differentvariable type. So, if you place a decimal value into a decimal type variable, you’ll findeverything works fine. Further, if you place the value of one variable into another of thesame type, your program works.