C# String Theory—ToString method

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C# String Theory Introduction § String Class § String Manipulation § StringBuilder Class § String Performance Optimization § String Tips and Tricks § String intern pool C# vs. Java strings ToString method

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Contents 1 ToString method 1.1 Printing numbers 1.2 1 Section 1.3 2 Sections 1.4 3 Sections 2 MSDN references

ToString method

One of the most used methods when creating strings is the .ToString() method. Looking a little deeper you will find that value types have 4 versions of this method which allow for greater string formatting control.

Printing numbers

When printing numbers you may find yourself coding statements such as this:

if (imaginary >= 0)
{
   strTemp = String.Format("{0}+{1}i", real, imaginary);
}
else
{
   strTemp = String.Format("{0}{1}i", real, imaginary);
}

However, with the .ToString(string format) statement, one can simplify the above to just one single line by removing the if statement and using sections of the format string instead.

strTemp = String.Format("{0}{1}i", real.ToString("#;-#;+0"), 
      imaginary.ToString("+#;-#;+0"))

The easiest way to understand sections is to think of the possible states of the value:

Sections are defined using the ; format specifier, when this is not used there is by default only one section. Therefore all 3 states' formatting are done in just the one section and so the same formatting is applied no matter what the state. As you may have guessed, up to 3 sections may be added corresponding to each state. The following pieces of code indicates how the states are formatted depending on the number of sections defined in the format string.

1 Section

int myNumber = 5;
   myNumber.ToString ("state 3 & state 2 & state 1");

2 Sections

int myNumber = 5;
   myNumber.ToString ("state 3 & state 2 ; state 1");

3 Sections

int myNumber = 5;
   myNumber.ToString ("state 3; state 1; state 2");

MSDN references

• Standard Numeric Format Strings
• Custom Numeric Format Strings