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String interpolation: How do I make this function work with any type

This is a function to work with lists in string interpolation. It takes a List and an inner Func, and it appends the string result of the inner Func called for each member of the list, with a separator.
So the following builds a valid start of an Insert statement...
static void Main(string[] args)
{
var tableName = "customers";
var cols = new List<dynamic>
{
new { Name = "surname"},
new { Name = "firstname"},
new { Name = "dateOfBirth"}
};
Func<List<dynamic>, Func<dynamic, string>, string, string> ForEach = (list, func, separator) =>
{
var bldr = new StringBuilder();
var first = true;
foreach (var obj in list)
{
if (!first)
bldr.Append(separator);
first = false;
bldr.Append(func(obj));
}
return bldr.ToString();
};
var InsertStatement = $"Insert into { tableName } ( {ForEach(cols, col => col.Name, ", ")} )";
Console.WriteLine(InsertStatement);
Console.ReadLine();
}
Outputs...
Insert into customers ( surname, firstname, dateOfBirth )
It works for dynamic. How do I make it work for any type? The outer Func shouldn't care about the Type in the list, it just passes it through to the inner Func.

The .NET framework already gives you a generic function to achieve what you are trying to do String.Join and you can combine it with a LINQ Select statement, which will allow you to use a lambda on a generic type to select the property that you want to print. You can view the source code of these methods if you are interested as they are open source.
using System;
using System.Collections.Generic;
using System.Linq;
public class MyType
{
public string Name { get; set; }
}
public class Program
{
public static void Main()
{
var tableName = "customers";
var cols = new List<MyType>
{
new MyType { Name = "surname"},
new MyType { Name = "firstname"},
new MyType { Name = "dateOfBirth"}
};
var InsertStatement = $"Insert into { tableName } ( {String.Join(", ", cols.Select(col => col.Name))} )";
Console.WriteLine(InsertStatement);
}
}

Replace dynamic with object, or TValue with a type constraint stipulating it must be a class (where TValue : class), and call obj.ToString() instead of just obj
However, this doesn't guarantee it would "work with any type" - for that you need to know that those types all follow a contract to output the desired column name as their string representation. To get more specificity, require that your accepted types must implement some interface eg IColumnName and put that interface into the type constraint instead

You can create the text easily like this:
var query = $"INSERT INTO {tableName}({string.Join(",", cols.Select(x=>x.Name))})";
However, if for learning purpose you are going to handle the case using a generic method, you can create a generic function like the following and then easily use a for loop and strip additional separator using TrimEnd, or as a better option, like String.Join implementation of .NET Framework get enumerator like this:
string Join<TItem>(
IEnumerable<TItem> items, Func<TItem, string> itemTextSelecor, string separator)
{
var en = items.GetEnumerator();
if (!en.MoveNext())
return String.Empty;
var builder = new StringBuilder();
if (en.Current != null)
builder.Append(itemTextSelecor(en.Current));
while (en.MoveNext())
{
builder.Append(separator);
if (en.Current != null)
builder.Append(itemTextSelecor(en.Current));
}
return builder.ToString();
}
And use it this way:
var tableName = "customers";
var cols = new[]
{
new { Name = "surname"},
new { Name = "firstname"},
new { Name = "dateOfBirth"}
};
var InsertStatement = $"INSERT INTO {tableName} ({Join(cols, col => col.Name, ", ")})"
+ $"VALUES({Join(cols, col => $"#{col.Name}", ", ")})";

Sensible way to output content of dictionary as valid html tags?

I am trying to generate hreflang tags like so:
<link hreflang="en-DE" rel="alternate" href="/en-DE" />
I currently am putting together my dictionary as below, and I thought I could use a 2nd foreach loop to generate the tags with the key value pairs:
public static IHtmlString HrefLangLinks(this PageData currentPage)
{
var hrefLangTags = string.Empty;
var availablePageLanguages = currentPage.ExistingLanguages.Select(culture => culture.Name).ToArray();
Dictionary<string, string> langs = new Dictionary<string, string>();
var contentLoader = ServiceLocator.Current.GetInstance<IContentLoader>();
var urlResolver = ServiceLocator.Current.GetInstance<UrlResolver>();
foreach (string cultureName in availablePageLanguages)
{
var culturePage = contentLoader.Get<PageData>(currentPage.ContentGuid, new LanguageSelector(cultureName));
var culturePath = urlResolver.GetVirtualPath(culturePage.ContentLink, culturePage.Language.Name);
langs.Add(cultureName, culturePath.GetUrl());
foreach (KeyValuePair<string, string> entry in langs)
{
hrefLangTags += ("<link hreflang=\"{0}\" rel=\"alternate\" href=\"{1}\" >", langs.Keys, langs.Values);
}
}
return new HtmlString(hrefLangTags);
}
Is there a simple and elegant way to iterate through the dictionary and create my tags?

Why are you even using a dictionay? You could just iterate through "availablePageLanguages" and append the needed data to your "hrefLangTags".
So like this:
public static IHtmlString HrefLangLinks(this PageData currentPage)
{
var hrefLangTags = string.Empty;
var availablePageLanguages = currentPage.ExistingLanguages.Select(culture => culture.Name).ToArray();
var contentLoader = ServiceLocator.Current.GetInstance<IContentLoader>();
var urlResolver = ServiceLocator.Current.GetInstance<UrlResolver>();
foreach (string cultureName in availablePageLanguages)
{
var culturePage = contentLoader.Get<PageData>(currentPage.ContentGuid, new LanguageSelector(cultureName));
var culturePath = urlResolver.GetVirtualPath(culturePage.ContentLink, culturePage.Language.Name);
hrefLangTags += String.Format("<link hreflang=\"{0}\" rel=\"alternate\" href=\"{1}\" >", culturName, culturePath.GetUrl());
}
return new HtmlString(hrefLangTags);
}

Your method does not make use of the first principle of SOLID (Single responsibility). You want to return links based on data input. But you are generating the needed data in the same method that is responsible for converting it to a list of IHtmlStrings.
The code beneath is may not be compact but it's a bit easier to read because the nested foreach loop is removed. You could call the method below by chaining them like: CreateLanguageLinksList(CreateWorkingLanguageDictionary(currentPage)) or do it like so
var languageDictionary = CreateWorkingLanguageDictionary(currentPage);
var listOfIHtmlStrings = CreateLanguageLinksList(languageDictionary);
The code above is easier to read, so the cognetive load is less straining on the mind.
public Dictionary<string, string> CreateWorkingLanguageDictionary(this PageData currentPage)
{
var languageDictionary = new Dictionary<string, string>();
var contentLoader = ServiceLocator.Current.GetInstance<IContentLoader>();
var urlResolver = ServiceLocator.Current.GetInstance<UrlResolver>();
foreach (string cultureName in availablePageLanguages)
{
var culturePage = contentLoader.Get<PageData>(currentPage.ContentGuid, new LanguageSelector(cultureName));
var culturePath = urlResolver.GetVirtualPath(culturePage.ContentLink, culturePage.Language.Name);
languageDictionary.Add(cultureName, culturePath.GetUrl());
}
return languageDictionary;
}
public IList<IHtmlString> CreateLanguageLinksList(Dictionary<string, string> langs)
{
var htmlStringList = new List<IHtmlString>();
foreach (KeyValuePair<string, string> entry in langs)
{
htmlStringList.add(new HtmlString("<link hreflang=\"{0}\" rel=\"alternate\" href=\"{1}\" >", langs.Keys, langs.Values));
}
return htmlStringList;
}

Just for fun, you could do it in linq, it's a little more succinct:
public static IHtmlString HrefLangLinks(this PageData currentPage)
{
var contentLoader = ServiceLocator.Current.GetInstance<IContentLoader>();
var urlResolver = ServiceLocator.Current.GetInstance<UrlResolver>();
var links = currentPage.ExistingLanguages.Select(culture =>
{
var culturePage = contentLoader.Get<PageData>(currentPage.ContentGuid, new LanguageSelector(culture.Name));
var culturePath = urlResolver.GetVirtualPath(culturePage.ContentLink, culturePage.Language.Name);
return $"<link hreflang=\"{culture.Name}\" rel=\"alternate\" href=\"{culturePath.GetUrl()}\" >";
});
return new HtmlString(string.Join("",links));
}
Disclaimer: This is totally untested or verified.

Pass query result to method (Linq, Wpf)

I have method to save all values from table to txt file:
UserDataDBsDataContext dataContext = new UserDataDBsDataContext();
List<UserData> usersL = (from u in dataContext.UserDatas
select u).ToList();
var properties = typeof(UserData).GetProperties();
var userValues = new List<string>();
foreach (var user in usersL)
{
var values = new List<object>();
foreach (var property in properties)
{
object value = property.GetValue(user, null);
values.Add(value);
}
userValues.Add(string.Join(",", values));
}
File.WriteAllLines("my_data.txt", userValues);
Now I have two query and I want to do exactly the same, so I tried to create separate method responsible for looping table values.
Loop Method:
public void loopProp(PropertyInfo[] properites, List<string> addedValues)
{
foreach (var qrl in ...........)
{
var values = new List<object>();
foreach (var property in properites)
{
object value = property.GetValue(qrl, null);
values.Add(value);
}
addedValues.Add(string.Join(",", values));
}
File.WriteAllLines("my_passed_data.txt", addedValues);
}
But I don't know, how to pass query result(ar or ud):
My code:
List<AutoRef> ar = (from a in rjdc.AutoRefs
select a).ToList();
List<UserDataRef> ud = (from u in rjdc.UserDataRefs
select u).ToList();
var propertiesAutoRef = typeof(AutoRef).GetProperties();
var autoValues = new List<string>();
var propertiesUserRef = typeof(UserDataRef).GetProperties();
var userValues = new List<string>();
//loopProp(propertiesAutoRef, autoValues);
//loopProp(propertiesUserRef, userValues);

Answering your concrete question. You should make the method generic and pass the source as IEnumerable<T>:
public void loopProp<T>(IEnumerable<T> source, PropertyInfo[] properites, List<string> addedValues)
{
foreach (var qrl in source)
{
// ...
}
File.WriteAllLines("my_passed_data.txt", addedValues);
}
Usage:
loopProp(ar, propertiesAutoRef, autoValues);
loopProp(ud, propertiesUserRef, userValues);
Probably you should pass the file path argument as well instead of hardcoding it inside the method.

Create c# dynamic object from elements of a list

how to convert :
A List :
var list = new List<string>(){"str1","str2"}
to a anonymous object :
var anonymousObject = new {str1 = "str1",str2 = "str2"}
during runtime

You can use the ExpandoObject which will give you the feature of dynamic type.
var list = new List<string>() { "str1", "str2" };
ExpandoObject obj = new ExpandoObject();
var store = (IDictionary<string, object>)obj;
list.ForEach(x => store.Add(x, x));
dynamic lst = obj;
var val = lst.str1; // Test

You can also use extension method represented below (from here).
Because converting list to dynamic object by iterating on items manually can be painful when there is many situations like this in your application.
You can use this extension method like this:
dynamic list = new List<string>() { "str1", "str2" }
.ToDictionary(dd => dd, dd => (object)dd)
.ToExpando();
The extension method:
public static ExpandoObject ToExpando(this IDictionary<string, object> dictionary)
{
var expando = new ExpandoObject();
var expandoDic = (IDictionary<string, object>)expando;
// go through the items in the dictionary and copy over the key value pairs)
foreach (var kvp in dictionary)
{
// if the value can also be turned into an ExpandoObject, then do it!
if (kvp.Value is IDictionary<string, object>)
{
var expandoValue = ((IDictionary<string, object>)kvp.Value).ToExpando();
expandoDic.Add(kvp.Key, expandoValue);
}
else if (kvp.Value is ICollection)
{
// iterate through the collection and convert any strin-object dictionaries
// along the way into expando objects
var itemList = new List<object>();
foreach (var item in (ICollection)kvp.Value)
{
if (item is IDictionary<string, object>)
{
var expandoItem = ((IDictionary<string, object>)item).ToExpando();
itemList.Add(expandoItem);
}
else
{
itemList.Add(item);
}
}
expandoDic.Add(kvp.Key, itemList);
}
else
{
expandoDic.Add(kvp);
}
}
return expando;
}

How to select multiple column from data base by getting column from user in .net

I have an object in my database, i.e. with 10 attributes.
Now I want to let the user select some of them (1 or 2 up to 10 of them) and then according by user's selection I make a list of object with the attributes selected by user
the scenario that I think about is this:
A page with check boxes that shows the attributes(columns) of that abject then user selects each of them he needs.
But here is my problem, how to make the selected check boxes run as query?
For example user selected col 1 , col 2, col 6 , col 10, how can I write a query responsible for user selection?
Example I wanna the meaningful phrase of this:
var file2 = file.Select(f => new { "attributes selected by user" }).OrderBy(what user wants)

they System.Linq.Dynamic library on Nuget is a way to go
[TestMethod]
public void StringyAndDangerous()
{
var fakePersonDbSet = new List<Person> { new Person() { FirstName = "Some", LastName = "Guy" } }.AsQueryable();
var attributes = new string[] { "FirstName", "LastName" };
var selectedFields = String.Join(",", attributes);
var exprssion = string.Format("new ({0})", selectedFields);
var result = fakePersonDbSet.Select(exprssion, attributes).Cast<dynamic>().First();
}
but you loose type safety and compile time checking. You might be better taking another approach
[TestMethod]
public void SlowerButSafer()
{
var fakePersonDbSet = new List<Person> { new Person() { FirstName = "Some", LastName = "Guy" } }.AsQueryable();
var attributes = new string[] { "FirstName", "LastName" };
var personPropertylist = CovertToKeyValuePair(fakePersonDbSet.First())
.Where(c=> attributes.Contains(c.Key))
.ToArray();
}
private IEnumerable<KeyValuePair<string, object>> CovertToKeyValuePair<T>(T #object)
{
var result = new List<KeyValuePair<string, object>>();
var properties = typeof (T).GetProperties();
foreach (var property in properties)
{
result.Add(new KeyValuePair<string, object>(property.Name, property.GetValue(#object, null)));
}
return result;
}
you'll take a performance hit both for pulling fields from the database that you don't need and for using reflection but the code will be less error prone and you won't end up with errors for trying to select columns that don't exist.

Use DynamicLinq. (link)
Extension methods:
public static T GetValue<T>(this DynamicClass dynamicObject, string propName)
{
if (dynamicObject == null)
{
throw new ArgumentNullException("dynamicObject");
}
var type = dynamicObject.GetType();
var props = type.GetProperties(BindingFlags.Public
| BindingFlags.Instance
| BindingFlags.FlattenHierarchy);
var prop = props.FirstOrDefault(property => property.Name == propName);
if (prop == null)
{
throw new InvalidOperationException("Specified property doesn't exist.");
}
return (T)prop.GetValue(dynamicObject, null);
}
public static string ToDynamicSelector(this IList<string> propNames)
{
if (!propNames.Any())
throw new ArgumentException("You need supply at least one property");
return string.Format("new({0})", string.Join(",", propNames));
}
Usage:
using System.Linq.Dynamic;
// ..
var columns = new[] { "col1", "col2", etc };
var result = context.Files.OrderBy(file => file.Id)
.Select(columns.ToDynamicSelector())
.Cast<DynamicClass>.ToList();
Result will be the collecion of DynamiClass instances wchich columns will contain selected properties.
To get single property from DynamicClass:
var columnValue = result.First().GetValue<string>("col1");
If you want to get values from IEnumerable:
var list = new List<File> { File1, File2, etc.. };
var result = list.AsQueryable().Select( /* the same as above */);