We Keep Coding

How to deal with a position in list that doesn't exist?

I'm building this program in C# in which you can enter membership details, confirm them, and view previously stored memberships. I am still very much a beginner and this is just some school homework.
My teacher suggested to write and read membership details to a file but I had no idea how to do this efficiently so just added them all to a list. I wrote this part to retrieve the username, password and membership type.
However, how do I stop an 'unhandled' error if the user enters a value in which doesn't have any stored data?
Here is the code: the list is called membersList.
Console.WriteLine("Which stored membership would you like to view? (e.g 1, 2..)");
int membChoice = Convert.ToInt32(Console.ReadLine());
Console.WriteLine("Membership Entry " + membChoice);
Console.WriteLine("Username: " + membersList[membChoice*3-3]);
Console.WriteLine("Password: " + membersList[membChoice*3-2]);
Console.WriteLine("Membership Type: " + membersList[membChoice*3-1].ToUpper());
This results in an unhandled exception error if you enter a larger value than members already stored.

You will first need to check if the list has an element at the position you want:
if(list.ElementAtOrDefault(membChoice*3-3) != null)
{
Console.WriteLine("Username: " + membersList[membChoice*3-3]);
}
That or you can do a try catch to catch the error and display something like invalid choice.

I don't think your list is efficient. I understand you save three information for the same object in three different indices.
I think a better way for comprehension when we begin to code, is to create a class for handle all of this information, like a Member class:
class Member
{
public int ID { get; set; }
public string Name { get; set; }
public string Password { get; set; }
public string Type { get; set; }
}
And use this class for ONLY ONE index of your list:
Member member = new Member()
{
ID = 0,
Name = "Monty Python",
Password = "My favorite color is blue",
Type = "Knight"
};
List<Member> membersList = new List<Member>();
membersList.Add(member);
After you can retrieve data by searching with ID:
User userFind = membersList.Find(x => x.ID == membChoice);
And then display data:
Console.WriteLine("UserName : " + userFind.Name);

Dynamic linq filter children using pivot

I have business objects that look like the following:
class Project
{
public int ID
{
get;set;
}
public string ProjectName
{
get;set;
}
public IList<ProjectTag> ProjectTags
{
get;set;
}
}
class ProjectTag
{
public int ID
{
get;set;
}
public int ProjectID
{
get;set;
}
public string Name
{
get;set;
}
public string Value
{
get;set;
}
}
Example Data:
Project:
ID ProjectName
1 MyProject
ProjectTags:
ID ProjectID Name Value
1 1 Name 1 Value 1
2 1 Name 2 Value 2
3 1 Name 3 Value 3
Basically it's a way for our users to define their own columns on the Project. As a result, it's important to remember that I don't know the names of the ProjectTag entries at design time.
What I'm trying to accomplish is to give our users the ability to select projects based on search criteria using System.Linq.Dynamic. For instance, to select just the project in my example above, our users could enter this:
ProjectName == "MyProject"
The more complicated aspect is applying a filter to the ProjectTags. Our application currently allow users to do this in order to filter Projects by their ProjectTags:
ProjectTags.Any(Name == "Name 1" and Value == "Value 1")
That works, but starts to get a bit messy for end users to use. Ideally I'd like to write something that would let them do the following:
Name 1 == "Value 1"
Or if necessary (due to white space in the name), something like the following...
[Name 1] == "Value 1"
"Name 1" == "Value 1"
For lack of a better explanation, it seems like I want to do the equivalent of a SQL pivot on the ProjectTags, and then still be able to execute a where clause against that. I've looked at some of the questions on StackOverflow about pivots and dynamic pivoting, but I haven't found anything too useful.
I've also been thinking about looping through all the ProjectTag Names and building a dynamic query using a left join on each. I guess something like this:
select
Project.*,
Name1Table.Value [Name 1],
Name2Table.Value [Name 2],
Name3Table.Value [Name 3]
from
Project
left join ProjectTag Name1Table on Name = 'Name 1'
left join ProjectTag Name2Table on Name = 'Name 2'
left join ProjectTag Name3Table on Name = 'Name 3'
And then take that query and apply a where clause to it. But I'm not really sure how to do that in Linq as well as dealing with the white space in the name.
I also came across ExpandoObject. I thought possibly I could convert Project to an ExpandoObject. Then loop through all known ProjectTag names, adding each name to the ExpandoObject and, if that Project had a ProjectTag for that name, use that ProjectTag value as the value, else empty string. For example...
private static object Expand(
Project project,
List<string> projectTagNames)
{
var expando = new ExpandoObject();
var dictionary = (IDictionary<string, object>) expando;
foreach (var property in project.GetType()
.GetProperties())
{
dictionary.Add(property.Name, property.GetValue(project));
}
foreach (var tagName in projectTagNames)
{
var tagValue = project.ProjectTags.SingleOrDefault(p => p.Name.Equals(tagName));
dictionary.Add(tagName, tagValue?.Value ?? "");
}
return expando;
}
The exciting thing about this solution is I have an object that looks exactly like I think it should prior to filtering with a where clause. It even seems to accommodate spaces in the property name.
Then of course I found out that dynamic linq doesn't work nicely with ExpandoObject, and so it can't find the dynamic properties. I guess that's because it essentially has a type of Object which isn't going to define any of the dynamic properties. Maybe it's possible to generate a type at run time that matches? Even if that works, I don't think it can account for spaces in the Name.
Am I trying to accomplish too much with this functionality? Should I just tell the users to use syntax like ProjectTags.Any(Name == "Name1" and Value == "Value1")? Or is there some way to trick dynamic linq into understanding ExpandoObject? Seems like having a way to override the way dynamic linq resolves property names would be very handy.

How about using a translator to convert tag references?
I assume that tag names containing spaces will be surrounded by brackets ([]) and that Project field names are a known list.
public static class TagTranslator {
public static string Replace(this string s, Regex re, string news) => re.Replace(s, news);
public static string Surround(this string src, string beforeandafter) => $"{beforeandafter}{src}{beforeandafter}";
public static string SurroundIfMissing(this string src, string beforeandafter) => (src.StartsWith(beforeandafter) && src.EndsWith(beforeandafter)) ? src : src.Surround(beforeandafter);
public static string Translate(string q) {
var projectFields = new[] { "ID", "ProjectName", "ProjectTags" }.ToHashSet();
var opREStr = #"(?<op>==|!=|<>|<=|>=|<|>)";
var revOps = new[] {
new { Fwd = "==", Rev = "==" },
new { Fwd = "!=", Rev = "!=" },
new { Fwd = "<>", Rev = "<>" },
new { Fwd = "<=", Rev = ">=" },
new { Fwd = ">=", Rev = "<=" },
new { Fwd = "<", Rev = ">" },
new { Fwd = ">", Rev = "<" }
}.ToDictionary(p => p.Fwd, p => p.Rev);
var openRE = new Regex(#"^\[", RegexOptions.Compiled);
var closeRE = new Regex(#"\]$", RegexOptions.Compiled);
var termREStr = #"""[^""]+""|(?:\w|\.)+|\[[^]]+\]";
var term1REStr = $"(?<term1>{termREStr})";
var term2REStr = $"(?<term2>{termREStr})";
var wsREStr = #"\s?";
var exprRE = new Regex($"{term1REStr}{wsREStr}{opREStr}{wsREStr}{term2REStr}", RegexOptions.Compiled);
var tq = exprRE.Replace(q, m => {
var term1 = m.Groups["term1"].Captures[0].Value.Replace(openRE, "").Replace(closeRE, "");
var term1q = term1.SurroundIfMissing("\"");
var term2 = m.Groups["term2"].Captures[0].Value.Replace(openRE, "").Replace(closeRE, "");
var term2q = term2.SurroundIfMissing("\"");
var op = m.Groups["op"].Captures[0].Value;
if (!projectFields.Contains(term1) && !term1.StartsWith("\"")) { // term1 is Name, term2 is Value
return $"ProjectTags.Any(Name == {term1q} && Value {op} {term2})";
}
else if (!projectFields.Contains(term2) && !term2.StartsWith("\"")) { // term2 is Name, term1 is Value
return $"ProjectTags.Any(Name == {term2q} && Value {revOps[op]} {term1})";
}
else
return m.Value;
});
return tq;
}
}
Now you just translate your query:
var q = "ProjectName == \"Project1\" && [Name 1] == \"Value 1\" && [Name 3] == \"Value 3\"";
var tq = TagTranslator.Translate(q);

Linq search not returning all entries

Guys i have two problems... firstly i have a linq query search that queries name and surname and returns the results from the db. eg .if i search John it will return John travolta which is perfect (my problem being) if i search john travolta the name and surname together it will find no result?... help.
Problem number 2: how do i clear the results of the search when i search again? because when i search the second time the results of the previous search is
public class SearchResults
{
public string Name { get; set; }
public string Surname { get; set; }
public SearchResults(string name, string surname)
{
Name = name;
Surname = surname;
}
protected void btnSearch_Click(object sender, EventArgs e)
{
string search = txtSearch.Text.ToLower().TrimEnd();
lsSearchResults = null;
lsSearchResults = new List<SearchResults>();
Repeater1.DataSource = null;
lsSearchResults.Clear();
Repeater1.DataSource = "";
}
if (string.IsNullOrWhiteSpace(txtSearch.Text))
{
lblResults.Text = "Please enter a password & Em#ilAddress";
lsSearchResults.Clear();
return;
}
else
{
var found = (from User in myDB.Memberships
where User.Name.ToLower().Contains(txtSearch.Text.ToLower()) ||
User.Surname.ToLower().Contains(txtSearch.Text.ToLower())
select new { User.Name, User.Surname });
// validates items in search query if Exist
if (!ChillZARdev.App_Code.Utilities.IsEmpty(found))
{
foreach (var user in found)
{
lsSearchResults.Add(new SearchResults(user.Name, user.Surname));
// ls.Add(user.Name + " " + user.Surname);
// Response.Write(user);
}
Repeater1.DataSource = lsSearchResults;
Repeater1.DataBind();
}
}

Short solution would be to include firstname and surname together in the where clause:
var found = (from User in myDB.Memberships
where User.Name.ToLower().Contains(txtSearch.Text.ToLower()) ||
User.Surname.ToLower().Contains(txtSearch.Text.ToLower()) ||
(User.Name + " " + User.Surname).ToLower().Contains(txtSearch.Text.ToLower())
However, this means a search for "Travolta john" wouldn't return any results.
If this matters you should split up the string by spaces, and search for each word.
List<string> searchSplit = txtSearch.Text.ToLower().Split(' ');
var found = (from User in myDB.Memberships
where IsMatch(searchSplit, User)
private bool IsMatch(List<string> searchSplit, User User){
return searchSplit.Count() ==
searchSplit.Where(x => User.Name.ToLower().Contains(x) ||
User.Surname.ToLower().Contains(x)).Count();
}
Ideally, as Steve B has commented, it would be best to implement a pre-built search engine which would require more tools for searching than a simple custom search would. But it depends on what your budget/requirements are.

var found = myDB.Memberships;
foreach(var word in txtSearch.Text)
{
var word2=word; //Must do this because word won't be right at execution
found=found.Where(u=>u.Name.Contains(word2) || u.Surname.Contains(word2));
}
I've removed the .ToLower, because the columns should already be marked as being case insensitive, and will be unless you've either changed it directly, or the default culture of the database.

A couple of months back, i was having the same problem, i was using singleton design pattern and the root problem was with the cache.. and for both of your problems there is one solution - you can try to clean the cache of a LINQ to SQL DataContext and you can do that by following way
public static void ClearCache(this DataContext context)
{
const BindingFlags FLAGS = BindingFlags.Instance | BindingFlags.Public | BindingFlags.NonPublic;
var method = context.GetType().GetMethod("ClearCache", FLAGS);
method.Invoke(context, null);
}
and you can call that method
public void DoWork()
{
//do work...
dataContext.ClearCache();
//do more work...
}
Hope it helps

Perform a linq expression for 'contains' with searching through a list for 'like' not exact matches

Okay so I am stumped and have looked around for this and I know I am doing the implementation of something very simple more complex than it needs to be. Basically I have a POCO object that will have a member that contains a string of other members. This is labeled as 'st' and it may have strings that are comma seperated series in one string. Thus I may have two members of strings be 'images, reports' and another 'cms, crm'. I have a list of objects that I want to match for PART OF those strings but not necessarily all as a DISTINCT LIST. So a member of 'cms' would return the value of anything that contained 'cms' thus 'cms, crm' would be returned.
I want to hook this up so a generic List can be queried but I cannot get it to work and was looking at other threads but there methods do not work in my case. I keep thinking it is something simple but I am missing it completely. Please let me know if anyone has better ideas. I was looking here but could not get the logic to apply correctly:
Linq query list contains a list
I keep trying methods of 'Select', 'SelectMany', 'Contains', 'Any', 'All' at different levels of scope of the continuations to no avail. Here is a simple excerpt of where I am at with a simple Console app example:
public class Program
{
public class StringModel
{
public string name { get; set; }
public string str { get; set; }
}
static void Main(string[] args)
{
string s = "";
List<StringModel> sm = new List<StringModel>
{
new StringModel
{
name = "Set1",
str = "images, reports"
},
new StringModel
{
name = "Set2",
str = "cms, crm"
},
new StringModel
{
name = "Set3",
str = "holiday, pto, cms"
}
};
sm.ForEach(x => s += x.name + "\t" + x.str + "\n");
var selected = new List<object> {"cms", "crm"};
s += "\n\nITEMS TO SELECT: \n\n";
selected.ForEach(x => s += x + "\n");
s += "\n\nSELECTED ITEMS: \n\n";
// works on a single item just fine
var result = sm.Where(p => p.str.Contains("cms")).Select(x => new { x.name, x.str}).ToList();
// I am not using select to get POCO on other methods till I can get base logic to work.
// Does not return anything
var result2 = sm.Where(p => selected.Any(x => x == p.str)).ToList();
// Does not return anything
var result3 = sm.Where(p => selected.Any(x => selected.Contains(p.str))).ToList();
result.ForEach(y => s += y + "\n");
s += "\n\n2nd SET SELECTED: \n\n";
result2.ForEach(y => s += y + "\n");
s += "\n\n3rd SET SELECTED: \n\n";
result3.ForEach(y => s += y + "\n");
Console.WriteLine(s);
Console.ReadLine();
}
}

result2 is empty because you're comparing an object (x) with a string (StringModel.str). This will be a reference comparison. Even if you convert x to a string, you'll be comparing each value in selected ("cms", "crm") with your comma-separated string values ("images, reports", "cms, crm", "holiday, pto, cms").
result3 is empty because selected ("cms", "crm") does not contain any of the string values ("images, reports", "cms, crm", "holiday, pto, cms"), although in this case at least the comparisons are value comparisons.
I think you're looking for something like:
var result = sm.Where(p => selected.Any(x => p.str.Contains((string)x)));

Splitting a list<> that each item contains comma separated strings and formatting it out

I have a simple class like this:
class QuickReport
{
public string DeviceName { get; set; }
public string GroupName { get; set; }
public string PinName { get; set; }
public override string ToString()
{
return DeviceName + "," + GroupName + "," + PinName;
}
}
Later I make a list of items with this class:
List<QuickReport> QR = new List<QuickReport>();
Later in my program it will fill up and when I save it in a text file it will be like this example:
HBM\D1,GND,10
HBM\D1,GND,12
HBM\D1,NT_IOp,115
HBM\D1,NT_IOp,117
HBM\D2,GND,8
HBM\D2,NT_IOp,115
HBM\D2,NT_IOp,116
Now I want to make a function to save the text file in more readable manner. That is formatting it by DEVICE, GROUPS and PINS. So the above example would result in:
HBM\D1
GND: 10, 12
NT_IOp: 115, 117
HBM\D2
GND: 8
NT_IOp: 115, 116
can you please help and give some ideas?
Thanks!

var query = QR.ToLookup(i=>i.DeviceName, i => new {i.GroupName, i.PinName})
.Select(i=>
new {DeviceName = i.Key,
Groups = i.ToLookup(g=>g.GroupName, g=>g.PinName)});
var sb = new StringBuilder();
foreach ( var device in query)
{
sb.AppendLine(device.DeviceName);
foreach ( var gr in device.Groups)
{
sb.Append(gr.Key + ": ");
sb.Append(String.Join(", ", gr.ToArray()));
sb.AppendLine();
}
sb.AppendLine();
}
var stringToWrite = sb.ToString();

As i understand you have tree structure, where Device have child Groups, and Groups have child pins.
You can create custom classes like this:
class Group
{
string Name;
//pins that belong to this group
List<string> pins;
}
class Device
{
string Name;
//groups that belong to this device
List<Group> Groups;
}
And than just collect it to List<Device> and serialize it using XML Serialization.

This isn't complete, but it should give you enough to go on. You'll still need to add your newlines, and remove trailing commas, etc.
// Make your key the device name
var qrHash = new Dictionary<string, List<QuickReport>>();
// Populate your QR Dictionary here.
var output = new StringBuilder();
foreach (var keyValuePair in qrHash)
{
output.Append(keyValuePair.Key);
var gnd = new StringBuilder("GND: ");
var nt = new StringBuilder("NT_IOp: ");
foreach (var qr in keyValuePair.Value)
{
gnd.Append(qr.GroupName);
nt.Append(qr.PinName);
}
output.Append(gnd);
output.Append(nt);
}

How about using the XmlSerializer to serialize and deserialize your class? This should provide some readable output.
http://msdn.microsoft.com/en-us/library/system.xml.serialization.xmlserializer.aspx

The quickest ways I can think of to do this would either be to loop over the List<> 3 times, eachtime checking on a seperate accessor, writing it out to a StringBuilder, then returning StringBuilder.ToString() from the function.
Or, you could use 3 stringbuilders to hold each accessor type, then push all 3 from the function on return.