Using .NET Core, I am trying to save and retrieve a JSON Array of the object from Redis using IDistributedCache. Below is my code for storing and reading from Redis cache:
public void Save(string key, object content, int duration)
{
string s;
if (content is string)
{
s = (string)content;
}
else
{
s = JsonConvert.SerializeObject(content);
}
duration = duration <= 0 ? DefaultCacheDuration : duration;
Cache.Set(key, Encoding.UTF8.GetBytes(s), new DistributedCacheEntryOptions()
{
AbsoluteExpiration = DateTime.Now + TimeSpan.FromSeconds(duration)
});
}
public T Get<T>(string key) where T : class
{
var c = Cache.Get(key);
if (c == null)
{
return null;
}
var str = Encoding.UTF8.GetString(c);
if (typeof(T) == typeof(string))
{
return str as T;
}
return JsonConvert.DeserializeObject<T>(str);
}
the object that I want to store is
public class RuleLoadCollection_Result
{
[Key]
public int RuleId { get; set; }
public string RuleName { get; set; }
}
In my biz logic, am saving the object like this
public IQueryable<RuleLoadCollection_Result> GetRuleLibrary()
{
var result = _dbClient.GetRuleLibrary();
_cache.Save("TestKey", result);
return result;
}
the output here is an Array of Object.
[{"ruleId":1,"ruleName":"a1"}]
What code should I write to return the same array of objects from cache? I tried a few options, most of them gave compile or runtime errors. After the bit of browsing, I tried below, it worked, but it is giving only the first element of the array.
public RuleLoadCollection_Result GetRuleLibraryFromCache()
{
return (_cache.Get<List<RuleLoadCollection_Result>>("TestKey").First());
}
output for this is
{"ruleId":1,"ruleName":"a1"}
which I understand why, but what c# should I write to JSON array back which I saved?
below code gives the runtime error
public IQueryable<RuleLoadCollection_Result> GetRuleLibraryFromCache()
{
return (_cache.Get<IQueryable<RuleLoadCollection_Result>>("TestKey"));
}
the runtime error is:
Cannot create and populate list type System.Linq.IQueryable`1[RuleLoadCollection_Result]. Path '', line 1, position 1.
This worked.
public IQueryable<RuleLoadCollection_Result> GetRuleLibraryFromCache()
{
var result = _cache.Get<IEnumerable<RuleLoadCollection_Result>>("TestKey").AsQueryable();
return result;
}
Related
Well, I would like to do my own benchmarking system like spark in Minecraft (https://github.com/lucko/spark):
I'm using Harmony lib (https://github.com/pardeike/Harmony) which allows me to interact/modify methods and allows me to add a Prefix/Postfix on each call that will help me out with this stack.
The basic structure has something similar to (https://github.com/pardeike/Harmony/issues/355):
[HarmonyPatch]
class MyPatches
{
static IEnumerable<MethodBase> TargetMethods()
{
return AccessTools.GetTypesFromAssembly(Assembly.GetExecutingAssembly())
.SelectMany(type => type.GetMethods())
.Where(method => method.ReturnType != typeof(void) && method.Name.StartsWith("Do"));
}
static void Prefix(out Stopwatch __state, MethodBase __originalMethod)
{
__state = Stopwatch.StartNew();
// ...
}
static void Postfix(Stopwatch __state, MethodBase __originalMethod)
{
__state.Stop();
// ....
}
}
The problem here is that the __originalMethod doesn't take care if it was called from A or B.
So for example, we had patched string.Join method. And the we call from A or B, where A or B, is the full callstack of this method.
So first, we need to assign a ID to this call, and we need to create a Tree-based structure (which is hard to serialize later), from here (https://stackoverflow.com/a/36649069/3286975):
public class TreeModel : Tree<TreeModel>
{
public int ID { get; set; }
public TreeModel() { }
public TreeModel(TreeModel parent) : base(parent) { }
}
public class Tree<T> where T : Tree<T>
{
protected Tree() : this(null) { }
protected Tree(T parent)
{
Parent=parent;
Children=new List<T>();
if(parent!=null)
{
parent.Children.Add(this as T);
}
}
public T Parent { get; set; }
public List<T> Children { get; set; }
public bool IsRoot { get { return Parent==null; } }
public T Root { get { return IsRoot?this as T:Parent.Root; } }
public T RecursiveFind(Predicate<T> check)
{
if(check(this as T)) return this as T;
foreach(var item in Children)
{
var result=item.RecursiveFind(check);
if(result!=null)
{
return result;
}
}
return null;
}
}
Now, the thing is that we need to fill the Tree as long as we iterate all the method and instructions got from Harmony. Forget about Harmony for a second, I will explain only two facts about it.
The lib allows you first to get all patched methods through IEnumerable<MethodBase> TargetMethods() so, you have the Assembly X passed through reflection and filtered all methods that are allowed to be patched (some of them broke Unity, so I decided to skip methods from UnityEngine., UnityEditor. and System.* namespaces).
And we have also the ReadMethodBody method (https://harmony.pardeike.net/api/HarmonyLib.PatchProcessor.html#HarmonyLib_PatchProcessor_ReadMethodBody_System_Reflection_MethodBase_) from a given MethodBase it returns all IL stack instructions.
So we can start to iterate over and over in order to get all instructions and fill the entire tree. This is what I wrote last night:
internal static class BenchmarkEnumerator
{
internal static Dictionary<MethodBase, int> Mappings { get; } = new Dictionary<MethodBase, int>();
internal static Dictionary<int, TreeModel> TreeIDs { get; } = new Dictionary<int, TreeModel>();
internal static Dictionary<MethodBase, BenchmarkTreeModel> TreeMappings { get; } = new Dictionary<MethodBase, BenchmarkTreeModel>();
private static HashSet<int> IDUsed { get; } = new HashSet<int>();
public static int GetID(this MethodBase method)
{
return GetID(method, out _);
}
public static int GetID(this MethodBase method, out bool contains)
{
// A > X = X1
// B > X = X2
if (!Mappings.ContainsKey(method))
{
var id = Mappings.Count;
Mappings.Add(method, Mappings.Count);
IDUsed.Add(id);
contains = false;
return id;
}
contains = true;
return Mappings[method];
}
public static int GetFreeID()
{
int id;
Random rnd = new Random();
do
{
id = rnd.Next();
} while (IDUsed.Contains(id));
IDUsed.Add(id);
return id;
}
public static BenchmarkCall GetCall(int id)
{
return TreeIDs[id]?.Call;
}
public static BenchmarkCall GetCall(this MethodBase method)
{
return TreeIDs[Mappings[method]]?.Call;
}
}
The BenchmarkEnumerator class allow us to differentiate between A or B, but it doesn't care about the full hierarchy, only from the parent MethodBase itself, so I need to write something complex to take in care of the full call stack, which I said I have a problem to understand.
Then we have the TargetMethods:
private static IEnumerable<MethodBase> TargetMethods()
{
Model = new BenchmarkTreeModel();
var sw = Stopwatch.StartNew();
//int i = 0;
return Filter.GetTargetMethods(method =>
{
try
{
var instructions = PatchProcessor.ReadMethodBody(method);
var i = method.GetID(out var contains);
var tree = new TreeModel
{
ID = i
};
if (contains)
{
//var lastId = i;
i = GetFreeID();
tree.ID = i;
tree.FillMethodName($"{method.GetMethodSignature()}_{i}"); // TODO: Check this
tree.Parent = null;
tree.Children = TreeMappings[method].Forest.First().Children; // ??
//DictionaryHelper.AddOrAppend(TreeMappings, method, tree);
TreeMappings[method].Forest.Add(tree);
TreeIDs.Add(i, tree);
Model.Forest.Add(tree);
// UNIT TESTING: All contained methods at this point will have a parent.
// string.Join is being added as a method by a instruction, so when we try to patch it, it will have already a reference on the dictionary
// Here, we check if the method was already added by a instruction CALL
// Logic: If the method is already contained by the mapping dictionary
// then, we will exit adding a new that will have the same childs but a new ID
return false;
}
TreeIDs.Add(i, tree);
tree.FillMethodName($"{method.GetMethodSignature()}_{i}"); // TODO: Check this
foreach (var pair in instructions)
{
var opcode = pair.Key;
if (opcode != OpCodes.Call || opcode != OpCodes.Callvirt) continue;
var childMethod = (MethodBase)pair.Value;
var id = childMethod.GetID(out var _contains);
var subTree = new TreeModel(tree)
{
ID = id
};
if (_contains)
{
id = GetFreeID();
subTree.ID = id;
subTree.FillMethodName($"{childMethod.GetMethodSignature()}_{id}"); // TODO: Check this
subTree.Parent = TreeIDs[i];
subTree.Children = TreeMappings[childMethod].Forest.First().Children;
TreeIDs.Add(id, subTree);
continue;
}
TreeIDs.Add(id, subTree);
subTree.FillMethodName($"{childMethod.GetMethodSignature()}_{id}");
tree.Children.Add(subTree);
TreeMappings.Add(childMethod, new BenchmarkTreeModel());
TreeMappings[childMethod].Forest.Add(subTree);
}
TreeMappings.Add(method, new BenchmarkTreeModel());
TreeMappings[method].Forest.Add(tree);
Model.Forest.Add(tree);
return true;
//var treeModel = new TreeModel();
}
catch (Exception ex)
{
//Debug.LogException(new Exception(method.GetMethodSignature(), ex));
return false;
}
}, sw);
//return methods;
}
The GetMethodSignature is something like:
public static string GetMethodSignature(this MethodBase method)
{
if (method == null) return null;
return method.DeclaringType == null ? method.Name : $"{method.DeclaringType.FullName}.{method.Name}";
}
I think I'll replace it with the MethodBase.ToString instead (what do you think?)
Also, we have the BenchmarkCall class which allow us to take in care how many times the call was done and how many time it has spent at all:
[Serializable]
public class BenchmarkCall
{
public string Method { get; set; }
public double SpentMilliseconds { get; set; }
public long SpentTicks { get; set; }
public double MinSpentMs { get; set; } = double.MaxValue;
public double MaxSpentMs { get; set; } = double.MinValue;
public long MinSpentTicks { get; set; } = long.MaxValue;
public long MaxSpentTicks { get; set; } = long.MinValue;
public double AvgMs => SpentMilliseconds / TimesCalled;
public double AvgTicks => SpentTicks / (double)TimesCalled;
public BenchmarkCall()
{
}
public BenchmarkCall(MethodBase method)
{
Method = method.GetMethodSignature();
}
public override string ToString()
{
if (TimesCalled > 0)
return "BenchmarkCall{\n" +
$"Ticks[SpentTicks={SpentTicks},MinTicks={MinSpentTicks},MaxTicks={MaxSpentTicks},AvgTicks={AvgTicks:F2}]\n" +
$"Ms[SpentMs={SpentMilliseconds:F2},MinMs={MinSpentMs:F2},MaxMs={MaxSpentMs:F2},AvgMs={AvgMs:F2}]\n" +
"}";
return "BenchmarkCall{}";
}
}
}
So I think that my next movement will be to differentiate between X method being called from A or B (Xa or Xb) taking care of the full hierarchy (which I'm not sure how to do) instead of the parent method that calls it, maybe the code I wrote has some to do it with it, but I'm not sure (last night I was so tired, so I didn't code it taking care those facts), build up a list of method signatures with different IDs, and then fill up the tree, ID 1 is Xa and ID 2 is Xb (where I have problems also filling up the tree).
Also I'll need to use the Transpiler in order to alter all code instructions, so if a method has:
void method() {
X1();
X2();
}
We will need to add 2 methods (like prefix/postfix) to measure each instruction call:
void method() {
Start(1);
X1();
End(1);
Start(2);
X2();
End(2);
}
This will be a hard task, but I hope somebody could guide me with this out.
I am using a session helper class to track more than several variable. So far I have 30 that are needed from page to page, not all at once of course. I need to convert some of the values from single to array. The Session helper class I use is as follows. For brevity I have shown only two session variables we use for tracking tab index for two accordions.
using System;
using System.Globalization;
using System.Linq;
using System.Web;
public class SessionHelper
{
//Session variable constants
public const string AccordionTop = "#tabTop";
public const string AccordionBot = "#tabBot";
public static T Read<T>(string variable)
{
object value = HttpContext.Current.Session[variable];
if (value == null)
return default(T);
else
return ((T)value);
}
public static void Write(string variable, object value)
{
HttpContext.Current.Session[variable] = value;
}
public static int TabTop
{
get
{
return Read<int>(AccordionTop);
}
set
{
Write(AccordionTop, value);
}
}
public static int TabBot
{
get
{
return Read<int>(AccordionBot);
}
set
{
Write(AccordionBot, value);
}
}
}
So on each page I can work with variables easily as follows:
To Write:
SessionHelper.TabTop = 1; or SessionHelper.TabBot = 3
To Read:
If (SessionHelper.TabTop……….)
This all works fine. I now want to extend this to array values held in session. The array contains int, string and date time value.
For the array session object I have tried adding:
public class SessionHelper
{
public const string CompInfo = "CompAccInfo";
public static T ReadArray<T>(string variable)
{
object[] result = HttpContext.Current.Session[variable] as object[];
if (result == null)
{
return default(T);
//result = new object[30];
}
else
return ((T)(object)result);
}
public static void WriteArray(string variable, object[] value)
{
HttpContext.Current.Session[variable] = value;
}
public static object[] CompDetails
{
get
{
return ReadArray<object[]>(CompInfo);
}
set
{
WriteArray(CompInfo, value);
}
}
}
But then I get an “Object reference not set to…… error when I try to do this:
public void EGetCompanyInformation(MasterPage myMaster, int entityCode)
{
int prevEntity = 0;Using (sqlconnetiooo
.....
//I get values here this works fine
//Then:
sqlr = cmd.ExecuteReader();
sqlr.Read();
if (sqlr.HasRows)
{
//Calculate accounting period adjustment.
yearEndDiff = 12 - Convert.ToInt32(sqlr.GetDateTime(5).Month);
//Company Code.
SessionHelper.CompDetails[0] = sqlr.GetInt32(0);
//Company Name.
SessionHelper.CompDetails[1] = sqlr.GetString(1);
//Currency Unit.
SessionHelper.CompDetails[2] = sqlr.GetString(2);
//Base Currency Code.
SessionHelper.CompDetails[3] = sqlr.GetString(3);
//Reporting Currency Code.
SessionHelper.CompDetails[4] = sqlr.GetString(4);
//Company Year End.
SessionHelper.CompDetails[5] = yearEndDiff;
//Country Code.
SessionHelper.CompDetails[6] = sqlr.GetString(6);
//Country Name.
SessionHelper.CompDetails[7] = sqlr.GetString(7);
//Base Currency Name.
SessionHelper.CompDetails[8] = sqlr.GetString(8);
//Report Currency Name.
SessionHelper.CompDetails[9] = sqlr.GetString(9);
//ClientID.
SessionHelper.CompDetails[10] = sqlr.GetInt32(10);
Other code here
}
}
It seems any SessionHelper.CompDetails[i] does not work : Error Object reference not set to an instance of an object.
What will happen if ReadArray will return default(T)? It will return null. Than access to any object by index inside the array will cause the exception you face.
It is not quite obvious what your code is intended to do.
SessionHelper.CompDetails[0] = sqlr.GetInt32(0);
What do you want here? CompDetails itself should return an array. But you are trying to rewrite it immediately by some values.
If you want to access the CompDetails and rewrite it's objects than you have to instantiate it by
int n = 10;
SessionHelper.CompDetails = new CompDetails[n];
default(object[]) will always throw null. because the array of object is reference type and default value of any reference type is null. So accessing null value will get you Object reference not set to an instance of object.
You can change your old implementation like below:
public static T Read<T>(string variable, int arraySize=10)
{
object value = HttpContext.Current.Session[variable];
if(typeof(T).IsArray && value == null)
{
//array requires size I personally prefer to have
//differnt read method for array.
return ((T)Activator.CreateInstance(typeof(T),arraySize));
}
if(!typeof(T).IsValueType && value == null)
{
//if it is not value type you can return new instance.
return ((T)Activator.CreateInstance(typeof(T)));
}
else if (value == null)
return default(T);
else
return ((T)value);
}
And access SessionHelper as below:
var sessionarray = SessionHelper.Read<object[]>("myarray",15);
....
// then use that sessionarray here.
....
You have to instantiate the CompDetails array before you start assigning values to it.
if (sqlr.HasRows)
{
//Calculate accounting period adjustment.
yearEndDiff = 12 - Convert.ToInt32(sqlr.GetDateTime(5).Month);
// Instantiate array
SessionHelper.CompDetails = new object[11];
//Company Code.
SessionHelper.CompDetails[0] = sqlr.GetInt32(0);
// etc
This problem is affecting my ASP.Net WebApi Patch method which looks a lot like this:
public MyModel Patch(int id, [FromBody]Delta<MyModel> newRecord){/*stuff here*/}
But it's not WebApi that's the problem - the failure is between Json.Net and OData.Delta.
The problem is JsonConvert.DeserializeObject does not see integers of OData.Delta objects and I'm wondering if there's a workaround or fix I can apply.
UPDATE: Have written code (see right down below) in the Json.Net library that will fix this. Just need it to be included in the next update (if James Newton-King allows it)
UPDATE 2: After further testing, I've decided the best course of action is to stop using OData.Delta and write my own (see answer)
Unit tests to prove the problem exists (using statements moved below for clarity)
Test 1: Fails with an int (Int32):
class TestObjWithInt
{
public int Int { get; set; }
}
[TestMethod]
public void IsApplied_When_IntIsDeserializedToDelta()
{
string testData = "{\"Int\":1}";
var deserializedDelta = JsonConvert.DeserializeObject<Delta<TestObjWithInt>>(testData);
var result = deserializedDelta.GetChangedPropertyNames().Contains("Int");
Assert.IsTrue(result);
}
Test 2: Succeeds with a long (Int64)
class TestObjWithLong
{
public long Long { get; set; }
}
[TestMethod]
public void IsApplied_When_LongIsDeserializedToDelta()
{
string testData = "{\"Long\":1}";
var deserializedDelta = JsonConvert.DeserializeObject<Delta<TestObjWithLong>>(testData);
var result = deserializedDelta.GetChangedPropertyNames().Contains("Long");
Assert.IsTrue(result);
}
And just to be sure that deserialization works to begin with, these two tests both pass.
[TestMethod]
public void IsApplied_When_LongIsDeserializedToTestObject()
{
string testData = "{\"Long\":1}";
var deserializedObject = JsonConvert.DeserializeObject<TestObjWithLong>(testData);
var result = deserializedObject.Long == 1;
Assert.IsTrue(result);
}
[TestMethod]
public void IsApplied_When_IntIsDeserializedToTestObject()
{
string testData = "{\"Int\":1}";
var deserializedObject = JsonConvert.DeserializeObject<TestObjWithInt>(testData);
var result = deserializedObject.Int == 1;
Assert.IsTrue(result);
}
I found this OData bug report which sounds like a similar issue but its old and closed so probably not.
Any help would be great.
Using statements (from the top of the test file):
using System;
using System.Linq;
using System.Web.Http.OData;
using Microsoft.VisualStudio.TestTools.UnitTesting;
using Newtonsoft.Json;
Solution if accepted by James Newton-King - change to release 6.0.6.
Replace JsonSerializerInternalReader.cs line 1581:
contract.TrySetMember(newObject, memberName, value);
with:
bool done = false;
while (!(done = done || contract.TrySetMember(newObject, memberName, value)))
{
switch (reader.TokenType)
{
case JsonToken.Integer:
if (value is long && ((long)value) <= Int32.MaxValue && ((long)value) >= Int32.MinValue)
value = Convert.ToInt32(value);
//Add else if (...) to cast to other data types here (none additional required to date).
else
done = true;
break;
default:
done = true;
break;
}
}
OData.Delta<T> does not work with Json.Net for any number Types other than Int64. The easiest approach is to write a replacement for OData.Delta<T> (which I've done on company time so I can't post it in its entirety sorry) containing methods like this:
private bool TrySetInt32(object value, PropertyInfo propertyInfo, bool isNullable)
{
var done = false;
if (value is Int32)
{
propertyInfo.SetValue(_obj, value);
done = true;
}
else if (value == null)
{
if (isNullable)
{
propertyInfo.SetValue(_obj, value);
done = true;
}
}
else if (value is Int64) //Json.Net - fallback for numbers is an Int64
{
var val = (Int64)value;
if (val <= Int32.MaxValue && val >= Int32.MinValue)
{
done = true;
propertyInfo.SetValue(_obj, Convert.ToInt32(val));
}
}
else
{
Int32 val;
done = Int32.TryParse(value.ToString(), out val);
if (done)
propertyInfo.SetValue(_obj, val);
}
return done;
}
The class can be a dynamic generic like this:
public sealed class Patchable<T> : DynamicObject where T : class, new()
With a working variable like this:
T _obj = new T();
In the overridden TrySetMember method, we need to check the underlying type of the property using reflection and call the appropriate TrySet... method like this:
if (underlyingType == typeof(Int16))
done = TrySetInt16(value, propertyInfo, isNullable);
else if (underlyingType == typeof(Int32))
done = TrySetInt32(value, propertyInfo, isNullable);
If the value is set successfully we can add the property name to a list that we can then use for patching the original record like this:
if (done)
_changedPropertyNames.Add(propertyInfo.Name);
public void Patch(T objectToPatch)
{
foreach (var propertyName in _changedPropertyNames)
{
var propertyInfo = _obj.GetType().GetProperty(propertyName);
propertyInfo.SetValue(objectToPatch, propertyInfo.GetValue(_obj));
}
}
68 unit tests later, it all seems to work pretty well. Here's an example:
class TestObjWithInt32
{
public Int32 Int32 { get; set; }
public Int32? SetNullable { get; set; }
public Int32? UnsetNullable { get; set; }
}
[TestMethod]
public void IsApplied_When_Int32IsDeserializedToPatchable()
{
string testData = "{\"Int32\":1,\"SetNullable\":1}";
var deserializedPatchable = JsonConvert.DeserializeObject<Patchable<TestObjWithInt32>>(testData);
var result = deserializedPatchable.ChangedPropertyNames.Contains("Int32");
Assert.IsTrue(result);
var patchedObject = new TestObjWithInt32();
Assert.AreEqual<Int32>(0, patchedObject.Int32);
deserializedPatchable.Patch(patchedObject);
Assert.AreEqual<Int32>(1, patchedObject.Int32);
Assert.IsNull(patchedObject.UnsetNullable);
Assert.IsNotNull(patchedObject.SetNullable);
}
This is my implementation for this issue based on Rob solution:
public sealed class Patchable<T> : DynamicObject where T : class {
private readonly IDictionary<PropertyInfo, object> changedProperties = new Dictionary<PropertyInfo, object>();
public override bool TrySetMember(SetMemberBinder binder, object value) {
var pro = typeof (T).GetProperty(binder.Name);
if (pro != null)
changedProperties.Add(pro, value);
return base.TrySetMember(binder, value);
}
public void Patch(T delta) {
foreach (var t in changedProperties)
t.Key.SetValue(
delta,
t.Key.PropertyType.IsEnum ? Enum.Parse(t.Key.PropertyType, t.Value.ToString()) : Convert.ChangeType(t.Value, t.Key.PropertyType));
}
}
I removed the requisite of an empty constructor in generic type parameter using the dictionary instead of a temporal object.
Thanks Rob ;)
I have two variables that contain true/false data. THe first variable can be null but the second variable is always non null. Both variables will always be the same length.
var AnswerGridCorrect = "000111"; // or null
var AnswerGridResponses = "000011";
How could I change this data into an object oriented form. I already created classes and these are below. Here's is what I need the output to look like when converted to JSON:
"answers":[ // Json conversion made Answers into answers
{"correct":null,"response":true},
{"correct":null,"response":true},
{"correct":null,"response":true},
{"correct":null,"response":false}
}
Note that I am using LINQ to output the data so I think what I need is a function with parameters something like this:
.Select((t, index) => new {
Answer = t.Answer,
Answers = makeAnswer(t.AnswerGridCorrect,
t.AnswerGridResponses)
});
I am not sure if this helps but here were the classes I was using when I did this from JSON:
public class AnswerRow
{
public bool? Correct { get; set; }
public bool Response { get; set; }
}
public class AnswerRowList
{
public IList<AnswerRow> AnswerRows { get; set; }
}
Here is an implementation for your makeAnswers method:
public List<AnswerRow> makeAnswers(string c, string r)
{
var result = new List<AnswerRow>();
for(var i=0; i<r.Length; i++)
{
result.Add(
new AnswerRow {
Correct = c!=null?new Nullable<bool>(c[i]=='1'):null,
Response = r[i]=='1'
});
}
return result;
}
Rene's answer is probably correct, but here's the (unnecessarily complex) Linq way:
AnswerRowList MakeAnswer(string answerGridCorrect, string answerGridResponses)
{
return new AnswerRowList()
{
AnswerRows = answerGridResponses.Zip(
answerGridCorrect == null ?
Enumerable.Repeat<bool?>(null, answerGridResponses.Length) :
answerGridCorrect.Select(x => new Nullable<bool>(x == '1')),
(r, c) => new AnswerRow()
{
Correct = c,
Response = r == '1'
}).ToList()
};
}
I'm maintaining a legacy WebForms application and one of the pages just serves GET requests and works with many query string parameters. This work is done in the code-behind and does a lot of this type of check and casting.
protected override void OnLoad(EventArgs e)
{
string error = string.Empty;
string stringParam = Request.Params["stringParam"];
if (!String.IsNullOrEmpty(stringParam))
{
error = "No parameter";
goto LoadError;
}
Guid? someId = null;
try
{
someId = new Guid(Request.Params["guidParam"]);
}
catch (Exception){}
if (!someId.HasValue)
{
error = "No valid id";
goto LoadError;
}
// parameter checks continue on
LoadError:
log.ErrorFormat("Error loading page: {0}", error);
// display error page
}
I'd like to create a testable class that encapsulates this parsing and validation and moves it out of the code-behind. Can anyone recommend some approaches to this and/or examples?
As a first big step, I'd probably create some form of mapper/translator object, like this:
class SpecificPageRequestMapper
{
public SpecificPageRequest Map(NameValueCollection parameters)
{
var request = new SpecificPageRequest();
string stringParam = parameters["stringParam"];
if (String.IsNullOrEmpty(stringParam))
{
throw new SpecificPageRequestMappingException("No parameter");
}
request.StringParam = stringParam;
// more parameters
...
return request;
}
}
class SpecificPageRequest
{
public string StringParam { get; set; }
// more parameters...
}
Then your OnLoad could look like this:
protected override void OnLoad(EventArgs e)
{
try
{
var requestObject = requestMapper.Map(Request.Params);
stringParam = requestObject.StringParam;
// so on, so forth. Unpack them to the class variables first.
// Eventually, just use the request object everywhere, maybe.
}
catch(SpecificPageRequestMappingException ex)
{
log.ErrorFormat("Error loading page: {0}", ex.Message);
// display error page
}
}
I've omitted the code for the specific exception I created, and assumed you instantiate a mapper somewhere in the page behind.
Testing this new object should be trivial; you set the parameter on the collection passed into Map, then assert that the correct parameter on the request object has the value you expect. You can even test the log messages by checking that it throws exceptions in the right cases.
Assuming that you may have many such pages using such parameter parsing, first create a simple static class having extension methods on NamedValueCollection. For example,
static class Parser
{
public static int? ParseInt(this NamedValueCollection params, string name)
{
var textVal = params[name];
int result = 0;
if (string.IsNullOrEmpty(textVal) || !int.TryParse(textVal, out result))
{
return null;
}
return result;
}
public static bool TryParseInt(this NamedValueCollection params, string name, out int result)
{
result = 0;
var textVal = params[name];
if (string.IsNullOrEmpty(textVal))
return false;
return int.TryParse(textVal, out result);
}
// ...
}
Use it as follows
int someId = -1;
if (!Request.Params.TryParseInt("SomeId", out someId))
{
// error
}
Next step would be writing page specific parser class. For example,
public class MyPageParser
{
public int? SomeId { get; private set; }
/// ...
public IEnumerable<string> Parse(NamedValueCollection params)
{
var errors = new List<string>();
int someId = -1;
if (!params.TryParseInt("SomeId", out someId))
{
errors.Add("Some id not present");
this.SomeId = null;
}
this.SomeId = someId;
// ...
}
}