I'm doing some validation where I need to check for certain combinations between two values. For example, if string1 is "fruit", valid values for string2 are "apple", "banana" and "pear". Currently, I'm doing this:
switch(string1)
{
case "fruit":
if(string2 != "apple" && string2 != "banana")
{
return false;
}
break;
case "meat":
if(string2 != "beef" && string2 != "pork")
{
return false;
}
default:
return true;
break;
}
This is really two questions. The first is, is there any good way to do something more like this:
switch(string1)
{
case "fruit":
if(string2 NOT IN ("apple", "banana"))
{
return true;
}
break;
case "meat":
if(string2 NOT IN ("beef", "pork"))
{
return false;
}
default:
return true;
break;
}
The second part of this question is likely what will get answered first: is there a better/best way to do this? I'm not the most amazing coder in the world and this is the first "off the top of my head" solution, so I'm certainly open to better ones. Thanks!
A variation on Nick's answer. Create two lists and use the contains method against them.
public List<string> Fruit = new List<string>{"apple", "banana"};
public List<string> Meat = new List<string>{"beef", "pork"};
switch (string1)
{
case "fruit":
return Fruit.Contains(string2);
case "meat":
return Meat.Contains(string2);
}
Yeah, there's a better way. You want to create a map, which associates your "category" ("fruit") with a string List of your elements ("apple", "banana", etc.). Then you want to look up your "string1" in your example above from the map and see if your associated string List Contains() your "string2".
This makes it entirely data-driven, and leverages the built-in abilities of the Collections more successfully.
Here is a way using Linq:
Dictionary<string, IList<string>> validValues = new Dictionary<string, IList<string>>()
{
{ "fruit", new List<string>() { "apple", "banana" } },
{ "meat", new List<string>() { "pork", "beef" } }
};
if (validValues.FirstOrDefault(x => x.Key == string1 && x.Value.Contains(string2)).Value != null)
{
return true;
}
return false;
You can shorten your cases down to:
switch(string1)
{
case "fruit":
return new[] { "apple", "banana" }.Contains(string2);
case "meat":
return new[] { "beef", "pork" }.Contains(string2);
default:
return true;
break;
}
I think style is, to a large degree, dependent upon personal taste. This is my taste...I think it's easy to add a new value in there with the array style, with as little overhead (I believe, someone feel free to correct me) that you can get with an array/collection style of "if-in" type check.
You could do something like this:
Dictionary<string, string> map = new Dictionary<string, string>();
map.add("banana", "fruit");
map.add("apple", "fruit");
map.add("pear", "fruit");
map.add("beef", "meat");
map.add("pork", "meat");
if(map[string2] == string1)
return true;
Related
First of all I must say that I am pretty new using C#. I have written this code block to assign a value to a string var depending on the value of another var. I have used the Switch statement:
switch (_reader.GetString(0))
{
case "G":
permiso.Area = "General";
break;
case "SIS":
permiso.Area = "Sistems";
break;
case "SOP":
permiso.Area = "Development";
break;
case "HLP":
permiso.Area = "Support";
break;
}
Can I make this in an easier way in C#?
Thanks!
You can use Dictionary<string, string>(), which can store your "switch case" string as key and "switch case value" in value.
Example:
var dict = new Dictionary<string, string>()
{
{"G", "General"},
{"SIS", "Sistems"},
...
}
So your code in order to access will be:
var key = _reader.GetString(0);
if(dict.TryGetValue(key, out var value)
{
permiso.Area = value;
}
else
{
// handle not exists key situation
}
Modern C# has a pattern matching switch
permiso.Area = _reader.GetString(0) switch {
"G" => "General",
"SIS" => "Sistems",
"SOP" => "Development",
"HLP" => "Support",
_ => throw new InvalidOperationException($"The value {_reader.GetString(0)} is not handled")
};
C# will complain at you if you don't include the "else" at the end _ =>
I mean if exists in C# somo sentence that makes something like that: my_string=my_string.decode(old_value0,new_value0, old_value1,new_value1, ...)
If you're after something like Oracle's DECODE, you can write it:
string Decode(string expr, params string[] arr){
for(int i = 0; i < arr.Length; i+=2)
if(arr[i] == expr)
return arr[i+1];
return arr.Length % 2 == 0 ? null : arr[arr.Length-1];
}
You'd use it like:
permiso.Area = Decode(reader.GetString(0), "G", "General", "SIS", "Sistems", "SOP", "Development", "HLP", "Support");
If you want an ELSE, pass an odd length array (something after the "Support")
If you want to be able to call it on a string, such as reader.GetString(0).Decode("G" ...) you can declare it in a static class and precede the first argument with this :
static string Decode(this string expr, ....)
That will make it an extension method, so it can be called "on a string"
If you either have same mappings occur on multiple locations or generally use the same strings repeatingly (in conditions, e.g.), a more sophisticated and cleaner approach would be to use enums and their descriptions in the first place. This makes the code more readable as you can (and should) use the unique enum in the code and catch its description when needed.
You need this enum extension method to read enum descriptions:
using System;
using System.ComponentModel;
public static string Description(this Enum source) {
DescriptionAttribute[] attributes = (DescriptionAttribute[])source
.GetType()
.GetField(source.ToString())
.GetCustomAttributes(typeof(DescriptionAttribute), false);
return attributes.Length > 0 ? attributes[0].Description : string.Empty;
}
Prepare the enum and its corresponding dictionary mappers. If possible, those enums should only have one unique description but you can define additional mapper dictionaries to your likings, e.g. when you need a simple short to long text mapper as in your example.
using System.Collections.Generic;
using System.ComponentModel;
using System.Linq;
// enum and its description
public enum PermissionArea {
[Description("Development")]
Development = 1,
[Description("General")]
General,
[Description("Sistems")]
Sistems,
[Description("Support")]
Support
}
public static class MyEnumDicts {
// default mapping of enum to its description
public static readonly Dictionary<PermissionArea, string> PermissionAreaToText = new Dictionary<PermissionArea, string>() {
{ PermissionArea.Development, PermissionArea.Development.Description() },
{ PermissionArea.General, PermissionArea.General.Description() },
{ PermissionArea.Sistems, PermissionArea.Sistems.Description() },
{ PermissionArea.Support, PermissionArea.Support.Description() }
};
// mapping of enum to short text
// (only if needed as it is better to only use one unique
// value which is already set as description in the enum itself
public static readonly Dictionary<PermissionArea, string> PermissionAreaToShortText = new Dictionary<PermissionArea, string>() {
{ PermissionArea.Development, "SOP" },
{ PermissionArea.General, "G" },
{ PermissionArea.Sistems, "SIS" },
{ PermissionArea.Support, "Support" }
};
// add reverse mappers via linq
public static readonly Dictionary<string, PermissionArea> TextToPermissionArea = PermissionAreaToText.ToDictionary(m => m.Value, m => m.Key);
public static readonly Dictionary<string, PermissionArea> ShortTextToPermissionArea = PermissionAreaToShortText.ToDictionary(m => m.Value, m => m.Key);
}
The usage could be as follows:
public void MyMethod(string permissionAreaShortText) {
try {
// map to enum (no switch or ifs etc. needed here)
PermissionArea permissionArea = MyEnumDicts.ShortTextToPermissionArea[permissionAreaShortText];
// now you can work via enums and do not
// have to hassle with any strings anymore:
switch (permissionArea) {
case PermissionArea.Development: ...; break;
case PermissionArea.General: ...; break;
case PermissionArea.Sistems: ...; break;
case PermissionArea.Support: ...; break;
}
// output/use its description when needed:
string permissionAreaText = permissionArea.Description();
// ...
} catch (Exception ex) {
// error handling: short text is no permission area
// ...
}
}
I have some c# lines like this:
if (justification.Contains("CT_") ||
justification.Contains("CTPD_") ||
justification.Contains("PACS_") ||
justification.Contains("NMG_") ||
justification.Contains("TFS_ID") ||
justification.Contains("AX_") ||
justification.Contains("MR_") ||
justification.Contains("FALSE_POSITIVE") ||
justification.Contains("EXPLICIT_ARCH_TEAM_DESIGN_DECISON") ||
justification.Contains("EXPLICIT_ARCH_TEAM_DESIGN_DECISION"))
{
// justification is ok.
}else
{
reporter.Report(syntaxNode.GetLocation(), syntaxNode,
Resources.SpecifySuppressMessageJustificationTitle);
}
my idea was to put all these strings into an arra and at my IF Expression i just iterate my array (or enumerate an IEnumerable). But how can I Do this?
i started with this here:
IEnumerable<string> someValues = new List<string>() { "CT_", "CTPD","PACS_", "NMG_", "AX_" };
if (justification == BUT HOW I HAVE TO RUN THROUGH MY someValuesand get the
stringValues?)
{
}
you can do as below, if you need case insensitive contains check you can get upper case by using justification.ToUpper() since you already having value list in upper case
var someValues = new List<string>() { "CT_", "CTPD","PACS_", "NMG_", "AX_" };
if(someValues.Any(x=>justification.Contains(x))
{
// justification is ok.
}else
{
// not matching
}
var someValues = new[] { "CT_", "CTPD","PACS_", "NMG_", "AX_" };
if (someValues.Any(x => justification.Contains(x))
{
// justification is ok.
}
If justification is an IEnumerable(or a List), you can use Intersect
Intercept produces a set of items that can be found in both lists.
IEnumerable<string> someValues = new List<string>() { "CTPD","PACS_", "NMG_", "AX_"};
if (justification.Intersect(someValues).Any())
{
// Atleast one match was found.
}
If the justification variable is a string, you can use Any()
if(someValues.Any(x => justification.Contains(x))
{
// A match was found.
}
So I have a
if (toolStripTextBox1.Text.Contains("text1", "text2", "text3", ... "text139"
and then I started adding 139 items until I realized it didn't work
how would I overload the Contains method? Or just bypass the limit..
Use LINQ:
var items = new[]{"text1", "text2", "text3", ... "text139"};
if (items.Any(item => toolStripTextBox1.Text.Contains(item)) ...
Well, it's simply an AND operation. What you really want to achieve is to know whether a text simultaneously contains text1 AND text2 AND text3 and so forth. So simply you want str.Contains("text1") && str.Contains("text2").
But pretty much it seems like you are doing some code smell. However, we are not aware of the full scenario. It will be better to add all the parts in a collection, loop through it and check if the string contains each of the values.
If you want to check if your text box contains at least one word, you can stop on the first occurrence:
string[] words = { "text1", "text2", "text3" };
foreach (var word in words)
{
if (toolStripTextBox1.Text.Contains(word)) break;
}
If you want to check if your text box contains all the words, you need to stop on the first word which is not contained and flag that something's wrong:
string[] words = { "text1", "text2", "text3" };
bool allFound = true;
foreach (var word in words)
{
if (!toolStripTextBox1.Text.Contains(word))
{
allFound = false;
break;
}
}
if (allFound) { // }
This is exactly how Any() and All() extension methods from System.Linq work. So you can use them instead (less code)
string[] words = { "text1", "text2", "text3" };
if (words.All(w => toolStripTextBox1.Text.Contains(w))
{
// do smth if all words are contained
}
Or
string[] words = { "text1", "text2", "text3" };
if (words.Any(w => toolStripTextBox1.Text.Contains(w))
{
// do smth if at least one word is contained
}
You can build your own extension method of it some thing like:
public enum Operation
{
And,
Or
}
public static bool Contains(this string text,Operation operation,params string[] args)
{
switch(operation)
{
case Operation.And:
return args.All(item => text.Contains(item));
case Operation.Or:
return args.Any(item => text.Contains(item));
default:
return false;
}
}
and use it like
if(toolStripTextBox1.Text.Contains(Operation.And,"text1", "text2", "text3"))
OR
if(toolStripTextBox1.Text.Contains(Operation.Or,"text1", "text2", "text3"))
Consider this code:
switch (number)
{
case 1:
Number = (int)SmsStatusEnum.Sent;
break;
case 2:
Number = (int)SmsStatusEnum.Delivered;
break;
case 3:
Number = (int)SmsStatusEnum.Failed;
break;
default:
Number = (int)SmsStatusEnum.Failed;
break;
}
return Number;
I have a switch case that has default.So if the number is not 1,2 or 3 result to be Failed.
So i convert the code to delegate dictionary:
var statuses = new Dictionary<int, Func<SmsStatusEnum>>
{
{1,()=> SmsStatusEnum.Sent},
{2,()=> SmsStatusEnum.Delivered},
{3,()=> SmsStatusEnum.Failed},
};
How can I set default for delegate dictionary pattern?
To set a default you would just wrap the Dictionary in a function
SmsStatusEnum GetStatus(int value) {
Func<SmsStatusEnum> func;
if (!statuses.TryGetValue(value, out func)) {
// Default value
return SmsStatusEnum.Failed;
}
return func();
}
In this case though I don't quite see why you are storing a Func<SmsStatusEnum> here. Does the actual code involve computation in the Func<SmsStatusEnum> implementation? If so then this is indeed a good pattern. If not then you may want to consider just storing a Dictionary<int, SmsStatusEnum> directly
Sorry, but your solution looks bad for me. You don't need any extra dictionary to work with enums, you can create a new method and use Enum.TryParse method:
SmsStatusEnum GetStatus(int value)
{
SmsStatusEnum val;
if(Enum.TryParse<SmsStatusEnum>(value.ToString(), out val))
return val;
else
return SmsStatusEnum.Failed;
}
I go with this way:
var validStatues = new int[] {1, 3, 2};
if (!validStatues.Any(x=>x == statusId))
{
statusId = 0;
}
var statuses = new Dictionary<int, Func<SmsStatusEnum>>
{
{1,()=> SmsStatusEnum.Sent},
{2,()=> SmsStatusEnum.Delivered},
{3,()=> SmsStatusEnum.Failed},
{0,()=> SmsStatusEnum.Failed},
};
I have a lot of if, else if statements and I know there has to be a better way to do this but even after searching stackoverflow I'm unsure of how to do so in my particular case.
I am parsing text files (bills) and assigning the name of the service provider to a variable (txtvar.Provider) based on if certain strings appear on the bill.
This is a small sample of what I'm doing (don't laugh, I know it's messy). All in all, There are approximately 300 if, else if's.
if (txtvar.BillText.IndexOf("SWGAS.COM") > -1)
{
txtvar.Provider = "Southwest Gas";
}
else if (txtvar.BillText.IndexOf("georgiapower.com") > -1)
{
txtvar.Provider = "Georgia Power";
}
else if (txtvar.BillText.IndexOf("City of Austin") > -1)
{
txtvar.Provider = "City of Austin";
}
// And so forth for many different strings
I would like to use something like a switch statement to be more efficient and readable but I'm unsure of how I would compare the BillText. I'm looking for something like this but can't figure out how to make it work.
switch (txtvar.BillText)
{
case txtvar.BillText.IndexOf("Southwest Gas") > -1:
txtvar.Provider = "Southwest Gas";
break;
case txtvar.BillText.IndexOf("TexasGas.com") > -1:
txtvar.Provider = "Texas Gas";
break;
case txtvar.BillText.IndexOf("Southern") > -1:
txtvar.Provider = "Southern Power & Gas";
break;
}
I'm definitely open to ideas.
I would need the ability to determine the order in which the values were evaluated.
As you can imagine, when parsing for hundreds of slightly different layouts I occasionally run into the issue of not having a distinctly unique indicator as to what service provider the bill belongs to.
Why not use everything C# has to offer? The following use of anonymous types, collection initializers, implicitly typed variables, and lambda-syntax LINQ is compact, intuitive, and maintains your modified requirement that patterns be evaluated in order:
var providerMap = new[] {
new { Pattern = "SWGAS.COM" , Name = "Southwest Gas" },
new { Pattern = "georgiapower.com", Name = "Georgia Power" },
// More specific first
new { Pattern = "City of Austin" , Name = "City of Austin" },
// Then more general
new { Pattern = "Austin" , Name = "Austin Electric Company" }
// And for everything else:
new { Pattern = String.Empty , Name = "Unknown" }
};
txtVar.Provider = providerMap.First(p => txtVar.BillText.IndexOf(p.Pattern) > -1).Name;
More likely, the pairs of patterns would come from a configurable source, such as:
var providerMap =
System.IO.File.ReadLines(#"C:\some\folder\providers.psv")
.Select(line => line.Split('|'))
.Select(parts => new { Pattern = parts[0], Name = parts[1] }).ToList();
Finally, as #millimoose points out, anonymous types are less useful when passed between methods. In that case we can define a trival Provider class and use object initializers for nearly identical syntax:
class Provider {
public string Pattern { get; set; }
public string Name { get; set; }
}
var providerMap =
System.IO.File.ReadLines(#"C:\some\folder\providers.psv")
.Select(line => line.Split('|'))
.Select(parts => new Provider() { Pattern = parts[0], Name = parts[1] }).ToList();
Since you seem to need to search for the key before returning the value a Dictionary is the right way to go, but you will need to loop over it.
// dictionary to hold mappings
Dictionary<string, string> mapping = new Dictionary<string, string>();
// add your mappings here
// loop over the keys
foreach (KeyValuePair<string, string> item in mapping)
{
// return value if key found
if(txtvar.BillText.IndexOf(item.Key) > -1) {
return item.Value;
}
}
EDIT: If you wish to have control over the order in which elemnts are evaluated, use an OrderedDictionary and add the elements in the order in which you want them evaluated.
One more using LINQ and Dictionary
var mapping = new Dictionary<string, string>()
{
{ "SWGAS.COM", "Southwest Gas" },
{ "georgiapower.com", "Georgia Power" }
.
.
};
return mapping.Where(pair => txtvar.BillText.IndexOf(pair.Key) > -1)
.Select(pair => pair.Value)
.FirstOrDefault();
If we prefer empty string instead of null when no key matches we can use the ?? operator:
return mapping.Where(pair => txtvar.BillText.IndexOf(pair.Key) > -1)
.Select(pair => pair.Value)
.FirstOrDefault() ?? "";
If we should consider the dictionary contains similar strings we add an order by, alphabetically, shortest key will be first, this will pick 'SCE' before 'SCEC'
return mapping.Where(pair => txtvar.BillText.IndexOf(pair.Key) > -1)
.OrderBy(pair => pair.Key)
.Select(pair => pair.Value)
.FirstOrDefault() ?? "";
To avoid the blatant Schlemiel the Painter's approach that looping over all the keys would involve: let's use regular expressions!
// a dictionary that holds which bill text keyword maps to which provider
static Dictionary<string, string> BillTextToProvider = new Dictionary<string, string> {
{"SWGAS.COM", "Southwest Gas"},
{"georgiapower.com", "Georgia Power"}
// ...
};
// a regex that will match any of the keys of this dictionary
// i.e. any of the bill text keywords
static Regex BillTextRegex = new Regex(
string.Join("|", // to alternate between the keywords
from key in BillTextToProvider.Keys // grab the keywords
select Regex.Escape(key))); // escape any special characters in them
/// If any of the bill text keywords is found, return the corresponding provider.
/// Otherwise, return null.
string GetProvider(string billText)
{
var match = BillTextRegex.Match(billText);
if (match.Success)
// the Value of the match will be the found substring
return BillTextToProvider[match.Value];
else return null;
}
// Your original code now reduces to:
var provider = GetProvider(txtvar.BillText);
// the if is be unnecessary if txtvar.Provider should be null in case it can't be
// determined
if (provider != null)
txtvar.Provider = provider;
Making this case-insensitive is a trivial exercise for the reader.
All that said, this does not even pretend to impose an order on which keywords to look for first - it will find the match that's located earliest in the string. (And then the one that occurs first in the RE.) You do however mention that you're searching through largeish texts; if .NET's RE implementation is at all good this should perform considerably better than 200 naive string searches. (By only making one pass through the string, and maybe a little by merging common prefixes in the compiled RE.)
If ordering is important to you, you might want to consider looking for an implementation of a better string search algorithm than .NET uses. (Like a variant of Boyer-Moore.)
What you want is a Dictionary:
Dictionary<string, string> mapping = new Dictionary<string, string>();
mapping["SWGAS.COM"] = "Southwest Gas";
mapping["foo"] = "bar";
... as many as you need, maybe read from a file ...
Then just:
return mapping[inputString];
Done.
One way of doing it (other answers show very valid options):
void Main()
{
string input = "georgiapower.com";
string output = null;
// an array of string arrays...an array of Tuples would also work,
// or a List<T> with any two-member type, etc.
var search = new []{
new []{ "SWGAS.COM", "Southwest Gas"},
new []{ "georgiapower.com", "Georgia Power"},
new []{ "City of Austin", "City of Austin"}
};
for( int i = 0; i < search.Length; i++ ){
// more complex search logic could go here (e.g. a regex)
if( input.IndexOf( search[i][0] ) > -1 ){
output = search[i][1];
break;
}
}
// (optional) check that a valid result was found.
if( output == null ){
throw new InvalidOperationException( "A match was not found." );
}
// Assign the result, output it, etc.
Console.WriteLine( output );
}
The main thing to take out of this exercise is that creating a giant switch or if/else structure is not the best way to do it.
There are several approaches to do this, but for the reason of simplicity, conditional operator may be a choice:
Func<String, bool> contains=x => {
return txtvar.BillText.IndexOf(x)>-1;
};
txtvar.Provider=
contains("SWGAS.COM")?"Southwest Gas":
contains("georgiapower.com")?"Georgia Power":
contains("City of Austin")?"City of Austin":
// more statements go here
// if none of these matched, txtvar.Provider is assigned to itself
txtvar.Provider;
Note the result is according to the more preceded condition which is met, so if txtvar.BillText="City of Austin georgiapower.com"; then the result would be "Georgia Power".
you can use dictionary.
Dictionary<string, string> textValue = new Dictionary<string, string>();
foreach (KeyValuePair<string, string> textKey in textValue)
{
if(txtvar.BillText.IndexOf(textKey.Key) > -1)
return textKey.Value;
}