Every item about dengue would be returned, as would those that discuss both of the other two. Since dengue fever has been a concern for over 250 years, this search would yield different results. dengue OR ( malaria AND zika) = every article about dengue, or those that discuss both zika and malaria.Boolean searches allow you to combine words and phrases using the words AND, OR, NOT (known as Boolean operators) to limit, broaden, or define your search. As the zika virus has only recently been a serious issue, this would limit the number of results. FebruBoolean searching is built on a method of symbolic logic developed by George Boole, a 19th century English mathematician. When coming up with an effective patent search, it is important to understand the basics of Boolean searching, which ensures that you correctly define the. Every item returned would mention zika, and either dengue or malaria. ( dengue OR malaria) AND zika = articles about dengue or malaria, that also discuss zika.For example:ĭengue OR malaria AND zika can be interpreted as To make sure you get the search you want, use parentheses - every database follows those rules. Different databases have different rules about combining searches. Think of your search in concepts, then put those concepts inside parentheses. Searching on "dengue fever" will return only items with that exact phrase. If you're searching for a phrase rather than just a single word, you can group the words together with quotation marks. Note: sometimes AND NOT is used serves the same function as NOT. Searching on malaria NOT zika returns items that are about malaria, but will specifically NOT return items that contain the word zika. NOT eliminates items that contain the specified term.Searching on dengue OR malaria OR zika returns all items that contain any of the three search terms. OR searches find one term or the other.For example, searching on dengue AND malaria AND zika returns only results that contain all three search terms. There are three basic Boolean search commands: AND, OR and NOT.ĪND searches find all of the search terms. Using the correct Boolean operator can make all the difference in a successful search. C# language specificationįor more information, see The bool type section of the C# language specification.Boolean logic is a building block of many computer applications and is an important concept in database searching. For more information, see the Converting to and from Boolean values section of the System.Boolean API reference page. NET provides additional methods that you can use to convert to or from the bool type.
Those are an implicit conversion to the corresponding nullable bool? type and an explicit conversion from the bool? type. ConversionsĬ# provides only two conversions that involve the bool type. For more information, see the Nullable Boolean logical operators section of the Boolean logical operators article.įor more information about nullable value types, see Nullable value types. For the bool? operands, the predefined & and | operators support the three-valued logic. Use the nullable bool? type, if you need to support the three-valued logic, for example, when you work with databases that support a three-valued Boolean type. You can use the true and false literals to initialize a bool variable or to pass a bool value: bool check = true Ĭonsole.WriteLine(check ? "Checked" : "Not checked") // output: CheckedĬonsole.WriteLine(false ? "Checked" : "Not checked") // output: Not checked
The default value of the bool type is false. A bool expression can be a controlling conditional expression in the if, do, while, and for statements and in the conditional operator ?. The bool type is the result type of comparison and equality operators. To perform logical operations with values of the bool type, use Boolean logical operators. NET System.Boolean structure type that represents a Boolean value, which can be either true or false. The bool type keyword is an alias for the.
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