How do you test your Request QueryString variables

Question

I frequently make use of Request QueryString   variables   In my Page load I often do things like          int id   -1           if  Request QueryString  id      null                try                               id   int Parse Request QueryString  id                               catch                                  deal with it                                  DoSomethingSpectacularNow id     It all seems a bit clunky and rubbish  How do you deal with your Request QueryString  s

User · Accepted Answer

Below is an extension method that will allow you to write code like this:

int id = request.QueryString.GetValue<int>("id");
DateTime date = request.QueryString.GetValue<DateTime>("date");

It makes use of TypeDescriptor to perform the conversion. Based on your needs, you could add an overload which takes a default value instead of throwing an exception:

public static T GetValue<T>(this NameValueCollection collection, string key)
{
    if(collection == null)
    {
        throw new ArgumentNullException("collection");
    }

    var value = collection[key];

    if(value == null)
    {
        throw new ArgumentOutOfRangeException("key");
    }

    var converter = TypeDescriptor.GetConverter(typeof(T));

    if(!converter.CanConvertFrom(typeof(string)))
    {
        throw new ArgumentException(String.Format("Cannot convert '{0}' to {1}", value, typeof(T)));
    }

    return (T) converter.ConvertFrom(value);
}

User · Answer

Use int TryParse instead to get rid of the try-catch block   if   int TryParse Request QueryString  id    out id          error case

User · Answer

Try this dude     List lt string gt  keys   new List lt string gt  Request QueryString AllKeys     Then you will be able to search the guy for a string real easy via     keys Contains  someKey

User · Answer

Use int TryParse instead to get rid of the try-catch block   if   int TryParse Request QueryString  id    out id          error case

User · Answer

I actually have a utility class that uses Generics to  wrap  session  which does all of the  grunt work  for me  I also have something almost identical for working with QueryString values   This helps remove the code dupe for the  often numerous  checks    For example   public class QueryString       static NameValueCollection QS               get                       if  HttpContext Current    null                  throw new ApplicationException  No HttpContext                  return HttpContext Current Request QueryString                       public static int Int string key                int i           if   int TryParse QS key   out i               i   -1     Obviously Change as you see fit          return i                    Other types omitted        And to Use   void Test         int i   QueryString Int  test        NOTE   This obviously makes use of statics  which some people don t like because of the way it can impact test code   You can easily refactor into something that works based on instances and any interfaces you require   I just think the statics example is the lightest   Hope this helps gives food for thought

User · Answer

Use int TryParse instead to get rid of the try-catch block   if   int TryParse Request QueryString  id    out id          error case

User · Answer

I m using a little helper method   public static int QueryString string paramName  int defaultValue        int value      if   int TryParse Request QueryString paramName   out value           return defaultValue      return value      This method allows me to read values from the query string in the following way   int id   QueryString  id   0

User · Answer

Eeee this is a karma risk     I have a DRY unit-testable abstraction because  well  because there were too many querystring variables to keep on in a legacy conversion   The code below is from a utility class whose constructor requires a NameValueCollection input  this source  and the string array  keys  is because the legacy app was rather organic and had developed the possibility for several different strings to be a potential input key  However I kind of like the extensibility  This method inspects the collection for the key and returns it in the datatype required   private T GetValue lt T gt  string   keys        return GetValue lt T gt  keys  default T       private T GetValue lt T gt  string   keys  T vDefault        T x   vDefault       string v   null       for  int i   0  i  lt  keys Length  amp  amp  String IsNullOrEmpty v   i                  v   this source keys i               if   String IsNullOrEmpty v                 try                       x    typeof T  IsSubclassOf typeof Enum       T Enum Parse typeof T   v     T Convert ChangeType v  typeof T                      catch Exception e                          do whatever you want here                      return x

User · Answer

Eeee this is a karma risk     I have a DRY unit-testable abstraction because  well  because there were too many querystring variables to keep on in a legacy conversion   The code below is from a utility class whose constructor requires a NameValueCollection input  this source  and the string array  keys  is because the legacy app was rather organic and had developed the possibility for several different strings to be a potential input key  However I kind of like the extensibility  This method inspects the collection for the key and returns it in the datatype required   private T GetValue lt T gt  string   keys        return GetValue lt T gt  keys  default T       private T GetValue lt T gt  string   keys  T vDefault        T x   vDefault       string v   null       for  int i   0  i  lt  keys Length  amp  amp  String IsNullOrEmpty v   i                  v   this source keys i               if   String IsNullOrEmpty v                 try                       x    typeof T  IsSubclassOf typeof Enum       T Enum Parse typeof T   v     T Convert ChangeType v  typeof T                      catch Exception e                          do whatever you want here                      return x

User · Answer

if  string IsNullOrEmpty Request QueryString  id         querystring contains id

User · Answer

I do have functions for each  actually it s one small class  with lots of statics     GetIntegerFromQuerystring val  GetIntegerFromPost val         It returns -1 if fails  which is almost always OK for me  I have some other functions for negative numbers as well    Dim X as Integer   GetIntegerFromQuerystring  id   If x   -1 Then Exit Sub

User · Answer

You can use the extension methods below as well and do like this  int  id   Request  id   ToInt    if id HasValue            Extension methods  public static int  ToInt this string input         int val      if  int TryParse input  out val           return val      return null     public static DateTime  ToDate this string input        DateTime val      if  DateTime TryParse input  out val           return val      return null     public static decimal  ToDecimal this string input        decimal val      if  decimal TryParse input  out val           return val      return null

User · Answer

if  string IsNullOrEmpty Request QueryString  id         querystring contains id

User · Answer

I m using a little helper method   public static int QueryString string paramName  int defaultValue        int value      if   int TryParse Request QueryString paramName   out value           return defaultValue      return value      This method allows me to read values from the query string in the following way   int id   QueryString  id   0

User · Answer

You can use the extension methods below as well and do like this  int  id   Request  id   ToInt    if id HasValue            Extension methods  public static int  ToInt this string input         int val      if  int TryParse input  out val           return val      return null     public static DateTime  ToDate this string input        DateTime val      if  DateTime TryParse input  out val           return val      return null     public static decimal  ToDecimal this string input        decimal val      if  decimal TryParse input  out val           return val      return null

User · Answer

I do have functions for each  actually it s one small class  with lots of statics     GetIntegerFromQuerystring val  GetIntegerFromPost val         It returns -1 if fails  which is almost always OK for me  I have some other functions for negative numbers as well    Dim X as Integer   GetIntegerFromQuerystring  id   If x   -1 Then Exit Sub

User · Answer

You can use the extension methods below as well and do like this  int  id   Request  id   ToInt    if id HasValue            Extension methods  public static int  ToInt this string input         int val      if  int TryParse input  out val           return val      return null     public static DateTime  ToDate this string input        DateTime val      if  DateTime TryParse input  out val           return val      return null     public static decimal  ToDecimal this string input        decimal val      if  decimal TryParse input  out val           return val      return null

User · Answer

if  string IsNullOrEmpty Request QueryString  id         querystring contains id

User · Answer

I actually have a utility class that uses Generics to  wrap  session  which does all of the  grunt work  for me  I also have something almost identical for working with QueryString values   This helps remove the code dupe for the  often numerous  checks    For example   public class QueryString       static NameValueCollection QS               get                       if  HttpContext Current    null                  throw new ApplicationException  No HttpContext                  return HttpContext Current Request QueryString                       public static int Int string key                int i           if   int TryParse QS key   out i               i   -1     Obviously Change as you see fit          return i                    Other types omitted        And to Use   void Test         int i   QueryString Int  test        NOTE   This obviously makes use of statics  which some people don t like because of the way it can impact test code   You can easily refactor into something that works based on instances and any interfaces you require   I just think the statics example is the lightest   Hope this helps gives food for thought

User · Answer

Well for one thing use int TryParse instead     int id  if   int TryParse Request QueryString  id    out id         id   -1      That assumes that  not present  should have the same result as  not an integer  of course   EDIT  In other cases  when you re going to use request parameters as strings anyway  I think it s definitely a good idea to validate that they re present

User · Answer

Well for one thing use int TryParse instead     int id  if   int TryParse Request QueryString  id    out id         id   -1      That assumes that  not present  should have the same result as  not an integer  of course   EDIT  In other cases  when you re going to use request parameters as strings anyway  I think it s definitely a good idea to validate that they re present

User · Answer

Eeee this is a karma risk     I have a DRY unit-testable abstraction because  well  because there were too many querystring variables to keep on in a legacy conversion   The code below is from a utility class whose constructor requires a NameValueCollection input  this source  and the string array  keys  is because the legacy app was rather organic and had developed the possibility for several different strings to be a potential input key  However I kind of like the extensibility  This method inspects the collection for the key and returns it in the datatype required   private T GetValue lt T gt  string   keys        return GetValue lt T gt  keys  default T       private T GetValue lt T gt  string   keys  T vDefault        T x   vDefault       string v   null       for  int i   0  i  lt  keys Length  amp  amp  String IsNullOrEmpty v   i                  v   this source keys i               if   String IsNullOrEmpty v                 try                       x    typeof T  IsSubclassOf typeof Enum       T Enum Parse typeof T   v     T Convert ChangeType v  typeof T                      catch Exception e                          do whatever you want here                      return x

User · Answer

I do have functions for each  actually it s one small class  with lots of statics     GetIntegerFromQuerystring val  GetIntegerFromPost val         It returns -1 if fails  which is almost always OK for me  I have some other functions for negative numbers as well    Dim X as Integer   GetIntegerFromQuerystring  id   If x   -1 Then Exit Sub

User · Answer

You can use the extension methods below as well and do like this  int  id   Request  id   ToInt    if id HasValue            Extension methods  public static int  ToInt this string input         int val      if  int TryParse input  out val           return val      return null     public static DateTime  ToDate this string input        DateTime val      if  DateTime TryParse input  out val           return val      return null     public static decimal  ToDecimal this string input        decimal val      if  decimal TryParse input  out val           return val      return null

User · Answer

I modified Bryan Watts  answer so that if the param your asking does not exist and you have specified a nullable type it will return null    public static T GetValue lt T gt  this NameValueCollection collection  string key                if  collection    null                        return default T                      var value   collection key            if  value    null                       return default T                      var type   typeof T            if  type IsGenericType  amp  amp  type GetGenericTypeDefinition      typeof Nullable lt  gt                          type   Nullable GetUnderlyingType type                      var converter   TypeDescriptor GetConverter type            if   converter CanConvertTo value GetType                           return default T                      return  T converter ConvertTo value  type           You can now do this     Request QueryString GetValue lt int  gt  paramName     10

User · Answer

Eeee this is a karma risk     I have a DRY unit-testable abstraction because  well  because there were too many querystring variables to keep on in a legacy conversion   The code below is from a utility class whose constructor requires a NameValueCollection input  this source  and the string array  keys  is because the legacy app was rather organic and had developed the possibility for several different strings to be a potential input key  However I kind of like the extensibility  This method inspects the collection for the key and returns it in the datatype required   private T GetValue lt T gt  string   keys        return GetValue lt T gt  keys  default T       private T GetValue lt T gt  string   keys  T vDefault        T x   vDefault       string v   null       for  int i   0  i  lt  keys Length  amp  amp  String IsNullOrEmpty v   i                  v   this source keys i               if   String IsNullOrEmpty v                 try                       x    typeof T  IsSubclassOf typeof Enum       T Enum Parse typeof T   v     T Convert ChangeType v  typeof T                      catch Exception e                          do whatever you want here                      return x

User · Answer

I actually have a utility class that uses Generics to  wrap  session  which does all of the  grunt work  for me  I also have something almost identical for working with QueryString values   This helps remove the code dupe for the  often numerous  checks    For example   public class QueryString       static NameValueCollection QS               get                       if  HttpContext Current    null                  throw new ApplicationException  No HttpContext                  return HttpContext Current Request QueryString                       public static int Int string key                int i           if   int TryParse QS key   out i               i   -1     Obviously Change as you see fit          return i                    Other types omitted        And to Use   void Test         int i   QueryString Int  test        NOTE   This obviously makes use of statics  which some people don t like because of the way it can impact test code   You can easily refactor into something that works based on instances and any interfaces you require   I just think the statics example is the lightest   Hope this helps gives food for thought

User · Answer

if  string IsNullOrEmpty Request QueryString  id         querystring contains id

User · Answer

I modified Bryan Watts  answer so that if the param your asking does not exist and you have specified a nullable type it will return null    public static T GetValue lt T gt  this NameValueCollection collection  string key                if  collection    null                        return default T                      var value   collection key            if  value    null                       return default T                      var type   typeof T            if  type IsGenericType  amp  amp  type GetGenericTypeDefinition      typeof Nullable lt  gt                          type   Nullable GetUnderlyingType type                      var converter   TypeDescriptor GetConverter type            if   converter CanConvertTo value GetType                           return default T                      return  T converter ConvertTo value  type           You can now do this     Request QueryString GetValue lt int  gt  paramName     10

User · Answer

I actually have a utility class that uses Generics to  wrap  session  which does all of the  grunt work  for me  I also have something almost identical for working with QueryString values   This helps remove the code dupe for the  often numerous  checks    For example   public class QueryString       static NameValueCollection QS               get                       if  HttpContext Current    null                  throw new ApplicationException  No HttpContext                  return HttpContext Current Request QueryString                       public static int Int string key                int i           if   int TryParse QS key   out i               i   -1     Obviously Change as you see fit          return i                    Other types omitted        And to Use   void Test         int i   QueryString Int  test        NOTE   This obviously makes use of statics  which some people don t like because of the way it can impact test code   You can easily refactor into something that works based on instances and any interfaces you require   I just think the statics example is the lightest   Hope this helps gives food for thought

User · Answer

Well for one thing use int TryParse instead     int id  if   int TryParse Request QueryString  id    out id         id   -1      That assumes that  not present  should have the same result as  not an integer  of course   EDIT  In other cases  when you re going to use request parameters as strings anyway  I think it s definitely a good idea to validate that they re present

User · Answer

Well for one thing use int TryParse instead     int id  if   int TryParse Request QueryString  id    out id         id   -1      That assumes that  not present  should have the same result as  not an integer  of course   EDIT  In other cases  when you re going to use request parameters as strings anyway  I think it s definitely a good idea to validate that they re present

User · Answer

I m using a little helper method   public static int QueryString string paramName  int defaultValue        int value      if   int TryParse Request QueryString paramName   out value           return defaultValue      return value      This method allows me to read values from the query string in the following way   int id   QueryString  id   0

User · Answer

I m using a little helper method   public static int QueryString string paramName  int defaultValue        int value      if   int TryParse Request QueryString paramName   out value           return defaultValue      return value      This method allows me to read values from the query string in the following way   int id   QueryString  id   0

User · Answer

Use int TryParse instead to get rid of the try-catch block   if   int TryParse Request QueryString  id    out id          error case

User · Answer

Try this dude     List lt string gt  keys   new List lt string gt  Request QueryString AllKeys     Then you will be able to search the guy for a string real easy via     keys Contains  someKey

User · Answer

I do have functions for each  actually it s one small class  with lots of statics     GetIntegerFromQuerystring val  GetIntegerFromPost val         It returns -1 if fails  which is almost always OK for me  I have some other functions for negative numbers as well    Dim X as Integer   GetIntegerFromQuerystring  id   If x   -1 Then Exit Sub

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