Develop Reference

Create a 2-column List using a variable for list name

Because the original post (Create List with name from variable) was so old, I didn't want to approach this as an answer.
But, I wanted to add this use of the above solution because it was non-obvious to me. And, it may help some of my fellow noobs... Also, I ran into some issues I don't know how to address.
I needed a way to create a list using a variable name, in this case "mstrClock", for timing diagrams.
I was not able to get .NET to accept a two-column list, though, so I ended up with two dictionaries.
Is there a way to structure this so that I can use a single dictionary for both columns?
dictD.Add("mstrClock", new List<double>());
dictL.Add("mstrClock", new List<string>());
Then as I develop the timing diagram, I add to the lists as follows:
dictD["mstrClock"].Add(x); // This value will normally be the time value.
dictL["mstrClock"].Add("L"); // This value will be the "L", "F" or "H" logic level
Then to get at the data I did this:
for (int n = 0; n < dictD["mstrClock"].Count; n++)
{
listBox1.Items.Add(dictL["mstrClock"][n] + "\t" + dictD["mstrClock"][n].ToString());
}

Why not just store what you want to display, in the dictionary?
dict.Add("mstrClock", new List<string>());
dict["mstrClock"].Add($"L\t{x}");
for (int n = 0; n < dict["mstrClock"].Count; n++)
{
listBox1.Items.Add(dict["mstrClock"][n]);
}
On another point, do you even need a dictionary? What is the point of having a dictionary with one key? If you only need a List<string>, then only create that.
var items = new List<string>());
items.Add($"L\t{x}");
foreach (var item in items)
{
listBox1.Items.Add(item);
}

You can use Tuples in modern C# to create your two-column list as follows:
var list = new List<(double time, string logicLevel)>();
list.Add((1, "L"));
list.Add((2, "F"));
foreach (var element in list)
{
listBox1.Items.Add($"{element.time} \t {element.logicLevel}");
}
If using a dictionary is a must, you can change the above code to something like:
var dict = new Dictionary<string, List<(double time, string logicLevel)>>();
dict["mstrClock"] = new List<(double time, string logicLevel)>();
dict["mstrClock"].Add((1, "L"));
dict["mstrClock"].Add((2, "F"));
var list = dict["mstrClock"];
foreach (var element in list)
{
listBox1.Items.Add($"{element.time} \t {element.logicLevel}");
}

One approach to creating a 2-column list would be to create a list of key/value pairs:
var list = new List<KeyValuePair<double, string>();
list.Add(new KeyValuePair<double, string>(1, "L");
foreach (KeyValuePair<double, string> element in list)
{
listBox1.Items.Add($"{element.key} \t {element.value}");
}

Is there a way to loop through database using a datacontext to find and replace a value?

I have a list of email addresses that give a bumb if you send something to them, so they don't exist anymore. There a a lot of them and it is unclear where they are in a huge database.
Is there a way to loop through the database, through a datacontext, not knowing the table name or column name, and still find and replace the value?
I already have a collection of table names and column names put together (if needed)
I have tried a bunch of stuff like using reflection and other things.
Dictionary<string, List<string>> tablesWithColumns = new Dictionary<string, List<string>>();
var model = new System.Data.Linq.Mapping.AttributeMappingSource().GetModel(typeof(DataContext));
foreach (System.Data.Linq.Mapping.MetaTable modelTable in model.GetTables())
{
string tableName = modelTable.TableName;
tablesWithColumns.Add(tableName, new List<string>());
foreach (var dataMember in modelTable.RowType.DataMembers)
{
string columnName = dataMember.MappedName;
tablesWithColumns[tableName].Add(columnName);
}
}
Is there a way of using the following (pseudo):
string emailAdresThatHasToBeNull = "gmail#someemail.com";
using (DataContext dataContext = new DataContext())
{
foreach (KeyValuePair<string, List<string>> keyValuePair in tablesWithColumns)
{
string tableName = keyValuePair.Key;
foreach (string columnName in keyValuePair.Value)
{
var list = dataContext.(tableName).Columns(c => c.name == columnName).All(v => v == emailAdresThatHasToBeNull);
foreach (var entry in list)
{
entry = null;
}
}
}
dataContext.SubmitChanges();
}
The wanted result is everywhere the email address was is now NULL.

How do I remove duplicates from excel range? c#

I've converted cells in my excel range from strings to form a string list and have separated each item after the comma in the original list. I am starting to think I have not actually separated each item, and they are still one whole, trying to figure out how to do this properly so that each item( ie. the_red_bucket_01)is it's own string.
example of original string in a cell 1 and 2:
Cell1 :
the_red_bucket_01, the_blue_duck_01,_the green_banana_02, the orange_bear_01
Cell2 :
the_purple_chair_01, the_blue_coyote_01,_the green_banana_02, the orange_bear_01
The new list looks like this, though I'm not sure they are separate items:
the_red_bucket_01
the_blue_duck_01
the green_banana_02
the orange_bear_01
the_red_chair_01
the_blue_coyote_01
the green_banana_02
the orange_bear_01
Now I want to remove duplicates so that the console only shows 1 of each item, no matter how many there are of them, I can't seem to get my foreah/if statements to work. It is printing out multiple copies of the items, I'm assuming because it is iterating for each item in the list, so it is returning the data that many items.
foreach (Excel.Range item in xlRng)
{
string itemString = (string)item.Text;
List<String> fn = new List<String>(itemString.Split(','));
List<string> newList = new List<string>();
foreach (string s in fn)
if (!newList.Contains(s))
{
newList.Add(s);
}
foreach (string combo in newList)
{
Console.Write(combo);
}

You probably need to trim the strings, because they have leading white spaces, so "string1" is different from " string1".
foreach (string s in fn)
if (!newList.Contains(s.Trim()))
{
newList.Add(s);
}

You can do this much simpler with Linq by using Distinct.
Returns distinct elements from a sequence by using the default
equality comparer to compare values.
foreach (Excel.Range item in xlRng)
{
string itemString = (string)item.Text;
List<String> fn = new List<String>(itemString.Split(','));
foreach (string combo in fn.Distinct())
{
Console.Write(combo);
}
}
As mentioned in another answer, you may also need to Trim any whitespace, in which case you would do:
fn.Select(x => x.Trim()).Distinct()

Where you need to contain keys/values, its better to use Dictionary type. Try changing code with List<T> to Dictionary<T>. i.e.
From:
List<string> newList = new List<string>();
foreach (string s in fn)
if (!newList.Containss))
{
newList.Add(s);
}
to
Dictionary<string, string> newList = new Dictionary<string, string>();
foreach (string s in fn)
if (!newList.ContainsKey(s))
{
newList.Add(s, s);
}

If you are concerned about the distinct items while you are reading, then just use the Distinct operator like fn.Distinct()
For processing the whole data, I can suggest two methods:
Read in the whole data then use LINQ's Distinct operator
Or use a Set data structure and store each element in that while reading the excel
I suggest that you take a look at the LINQ documentation if you are processing data. It has really great extensions. For even more methods, you can check out the MoreLINQ package.

I think your code would probably work as you expect if you moved newList out of the loop - you create a new variable named newList each loop so it's not going to find duplicates from earlier loops.
You can do all of this this more concisely with Linq:
//set up some similar data
string list1 = "a,b,c,d,a,f";
string list2 = "a,b,c,d,a,f";
List<string> lists = new List<string> {list1,list2};
// find unique items
var result = lists.SelectMany(i=>i.Split(',')).Distinct().ToList();
SelectMany() "flattens" the list of lists into a list.
Distinct() removes duplicates.

var uniqueItems = new HashSet<string>();
foreach (Excel.Range cell in xlRng)
{
var cellText = (string)cell.Text;
foreach (var item in cellText.Split(',').Select(s => s.Trim()))
{
uniqueItems.Add(item);
}
}
foreach (var item in uniqueItems)
{
Console.WriteLine(item);
}

How to add string to an array list in c#

I have a list and a string
var Resnames= new List<string>();
string name = "something";
I want to append string to it like
Resnames += name;
How can I do it

Since you are using List (not a legacy fixed-size array) you able to use List.Add() method:
resourceNames.Add(name);
If you want to add an item after the instantiation of a list instance you can use object initialization (since C# 3.0):
var resourceNames = new List<string> { "something", "onemore" };
Also you might find useful List.AddRange() method as well
var resourceNames = new List<string>();
resourceNames.Add("Res1");
resourceNames.Add("Res2");
var otherNames = new List<string>();
otherNames.AddRange(resourceNames);

Just as simple as that:
Resnames.Add(name);
BTW: VisualStudio is your friend! By typing a . after Resnames it would have helped you.

try adding the string to array list like this,
var Resnames= new List<string>();
string name = "something";
Resnames.Add(name);
foreach (var item in Resnames)
{
Console.WriteLine(item);
}

Add String to List this way:
var ListName = new List<string>();
string StringName = "YourStringValue";
ListName.Add(StringName);

What's the pattern to use for iterating over associated sets of values?

It's pretty common - especially as you try to make your code become more data-driven - to need to iterate over associated collections. For instance, I just finished writing a piece of code that looks like this:
string[] entTypes = {"DOC", "CON", "BAL"};
string[] dateFields = {"DocDate", "ConUserDate", "BalDate"};
Debug.Assert(entTypes.Length == dateFields.Length);
for (int i=0; i<entTypes.Length; i++)
{
string entType = entTypes[i];
string dateField = dateFields[i];
// do stuff with the associated entType and dateField
}
In Python, I'd write something like:
items = [("DOC", "DocDate"), ("CON", "ConUserDate"), ("BAL", "BalDate")]
for (entType, dateField) in items:
# do stuff with the associated entType and dateField
I don't need to declare parallel arrays, I don't need to assert that my arrays are the same length, I don't need to use an index to get the items out.
I feel like there's a way of doing this in C# using LINQ, but I can't figure out what it might be. Is there some easy method of iterating across multiple associated collections?
Edit:
This is a little better, I think - at least, in the case where I have the luxury of zipping the collections manually at declaration, and where all the collections contain objects of the same type:
List<string[]> items = new List<string[]>
{
new [] {"DOC", "DocDate"},
new [] {"CON", "ConUserDate"},
new [] {"SCH", "SchDate"}
};
foreach (string[] item in items)
{
Debug.Assert(item.Length == 2);
string entType = item[0];
string dateField = item[1];
// do stuff with the associated entType and dateField
}

In .NET 4.0 they're adding a "Zip" extension method to IEnumerable, so your code could look something like:
foreach (var item in entTypes.Zip(dateFields,
(entType, dateField) => new { entType, dateField }))
{
// do stuff with item.entType and item.dateField
}
For now I think the easiest thing to do is leave it as a for loop. There are tricks whereby you can reference the "other" array (by using the overload of Select() that provides an index, for example) but none of them are as clean as a simple for iterator.
Here's a blog post about Zip as well as a way to implement it yourself. Should get you going in the meantime.

Create a struct?
struct Item
{
string entityType;
string dateField;
}
Pretty much the same as your Pythonic solution, except type-safe.

This is realy a variation on the other themes, but this would do the trick also...
var items = new[]
{
new { entType = "DOC", dataField = "DocDate" },
new { entType = "CON", dataField = "ConUserData" },
new { entType = "BAL", dataField = "BalDate" }
};
foreach (var item in items)
{
// do stuff with your items
Console.WriteLine("entType: {0}, dataField {1}", item.entType, item.dataField);
}

You can use the pair and a generic List.
List<Pair> list = new List<Pair>();
list.Add(new Pair("DOC", "DocDate"));
list.Add(new Pair("CON", "ConUserDate"));
list.Add(new Pair("BAL", "BalDate"));
foreach (var item in list)
{
string entType = item.First as string;
string dateField = item.Second as string;
// DO STUFF
}
Pair is part of the Web.UI, but you can easily create your own custom class or struct.

If you just want to declare the lists inline, you can do that in one step:
var entities = new Dictionary<string, string>() {
{ "DOC", "DocDate" },
{ "CON", "ConUserDate" },
{ "BAL", "BalDate" },
};
foreach (var kvp in entities) {
// do stuff with kvp.Key and kvp.Value
}
If they're coming from other things, we have a bunch of extension methods to build dictionaries from various data structures.