C Switch-case string starting with

Question

Is there any way to make a case condition in a switch statement where you say if a string begins with something   ex  Switch  mystring       case  abc     String begins with abc  abcd or abc1 or abcz or abc   or abc will fall in this condition           Do Something       break     default        break      UPDATE Other strings can be different length   abc    abczyv  dcs2   qwerty  as   k

User · Answer

This is now possible with C  7 0 s pattern matching  For example   var myString    abcDEF    switch myString        case string x when x StartsWith  abc              Do something here         break

User · Answer

If all the cases have the same length you can use switch  mystring SubString 0 Math Min len  mystring Length     Another option is to have a function that will return categoryId based on the string and switch on the id

User · Answer

Try this and tell my if it works hope it help you   string value   Convert ToString Console ReadLine      Switch value        Case  abc        break       default       break

User · Answer

Short answer  No   The switch statement takes an expression that is only evaluated once  Based on the result  another piece of code is executed   So what     String StartsWith is a function  Together with a given parameter  it is an expression  However  for your case you need to pass a different parameter for each case  so it cannot be evaluated only once   Long answer  1 has been given by others   Long answer  2   Depending on what you re trying to achieve  you might be interested in the Command Pattern Chain-of-responsibility pattern  Applied to your case  each piece of code would be represented by an implementation of a Command  In addition to the execute method  the command can provide a boolean Accept method  which checks whether the given string starts with the respective parameter   Advantage  Instead of your hardcoded switch statement  hardcoded StartsWith evaluations and hardcoded strings  you d have lot more flexibility   The example you gave in your question would then look like this   var commandList   new List lt Command gt      new MyABCCommand       foreach  Command c in commandList        if  c Accept mystring                 c Execute mystring           break           class MyABCCommand   Command       override bool Accept string mystring                return mystring StartsWith  abc

User · Answer

If the problem domain has some kind of string header concept  this could be modelled as an enum   switch GetStringHeader s         case StringHeader ABC          case StringHeader QWERTY                 StringHeader GetStringHeader string s        if  s StartsWith  ABC    return StringHeader ABC             enum StringHeader   ABC  QWERTY

User · Answer

If you knew that the length of conditions you would care about would all be the same length then you could   switch mystring substring 0  Math Min 3  mystring Length       case  abc         do something     break    case  xyz         do something else     break    default        do a different thing     break      The Math Min 3  mystring Length  is there so that a string of less than 3 characters won t throw an exception on the sub-string operation   There are extensions of this technique to match e g  a bunch of 2-char strings and a bunch of 3-char strings  where some 2-char comparisons matching are then followed by 3-char comparisons  Unless you ve a very large number of such strings though  it quickly becomes less efficient than simple if-else chaining for both the running code and the person who has to maintain it   Edit  Added since you ve now stated they will be of different lengths  You could do the pattern I mentioned of checking the first X chars and then the next Y chars and so on  but unless there s a pattern where most of the strings are the same length this will be both inefficient and horrible to maintain  a classic case of premature pessimisation    The command pattern is mentioned in another answer  so I won t give details of that  as is that where you map string patterns to IDs  but they are option   I would not change from if-else chains to command or mapping patterns to gain the efficiency switch sometimes has over if-else  as you lose more in the comparisons for the command or obtaining the ID pattern  I would though do so if it made code clearer   A chain of if-else s can work pretty well  either with string comparisons or with regular expressions  the latter if you have comparisons more complicated than the prefix-matches so far  which would probably be simpler and faster  I m mentioning reg-ex s just because they do sometimes work well with more general cases of this sort of pattern    If you go for if-elses  try to consider which cases are going to happen most often  and make those tests happen before those for less-common cases  though of course if  starts with abcd  is a case to look for it would have to be checked before  starts with abc

User · Answer

In addition to substring answer  you can do it as mystring SubString 0 3  and check in case statement if its  abc    But before the switch statement you need to ensure that your mystring is atleast 3 in length

[c#] C# Switch-case string starting with

Examples related to c#

Examples related to string

Examples related to switch-statement

Examples related to case