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c# calculate distinct value in datatable

what i have in my datatable
Resource
1 // 1 represent normal
1
2 // 2 represent sql
2
3 // 3 css
4 // 4 unicode
4
4
how can i perform calculation so that i could display the value in a textbox
normal 2
sql 2
css 1
unicode 3
total hits 9
what ive tried so far
var result = my_datatable.AsEnumerable().Sum(x => Convert.ToInt32(x["Resource"]));
string result2 = result.ToString();
totalTxtBox.Text = result2;
but it calculate the whole column (output is: 24 instead of 9)

Use the following example-
int[] res = { 1,1,2,2,3,4,4,4};
var words = res.AsEnumerable().GroupBy(x => x);
foreach (var x in words)
{
Console.WriteLine(x.Key+"-"+x.Count());
}
It will print output as-
1-2
2-2
3-1
4-3

You can try to use Distinct()
var result = my_datatable.AsEnumerable().Distinct().Sum(x => Convert.ToInt32(x["Resource"]));
Distinct() Returns distinct elements from a sequence by using the default equality comparer to compare values.
for more info: https://msdn.microsoft.com/en-us/library/bb348436(v=vs.110).aspx
You can try to use this example as your reference. Firstly, I get the Distinct values from the datatable and converted it to list and then use the sum function.
Updated Answer:
DataTable my_datatable = new DataTable();
my_datatable.Columns.Add("Value", typeof(int));
my_datatable.Columns.Add("Type", typeof(string));
my_datatable.Rows.Add(1, "Normal");
my_datatable.Rows.Add(1, "Normal");
my_datatable.Rows.Add(2, "SQL");
my_datatable.Rows.Add(2, "SQL");
my_datatable.Rows.Add(3, "CSS");
my_datatable.Rows.Add(4, "UNICODE");
my_datatable.Rows.Add(4, "UNICODE");
my_datatable.Rows.Add(4, "UNICODE");
var distinctIds = my_datatable.AsEnumerable()
.Select(s => new {
value = s.Field<int>("value"),
})
.Distinct().ToList();
int total = distinctIds.Sum(item => item.value);

I figured it out by myself
use this line (linq) in order to filter out which value you want
int normalcount = my_datatable
.AsEnumerable()
.Where(r => r.Field<string>("Resource") == "1")
.Count();
try to change this line to filter out which value, according to your column value
.Where(r => r.Field<string>("Resource") == "2")
.Count();

How to check DBNull value in Linq query results

I am using the below code and trying to group by Currency and Code. After this I am trying to loop through the result set.
But the issue is while looping through the results, at the end I am getting the below exception on the for each statement:
Object cannot be cast from DBNull to other types.
DataTable dt = new DataTable();
var result = from r in dt.AsEnumerable()
result r by new
{
currency = r.Field<String>("CURRENCY"),
Code = r.Field<String>("CODE")
}
into grp
select new
{
currency = grp.Key.currency,
Code = grp.Key.Code,
amount = grp.Sum(x => Convert.ToDouble(x["AMOUNT"]))
};
foreach (var obj in result)
{
String sCurr =obj.currency;
String Code = obj.Code;
string amount= obj.amount.ToString());
}
Please help me to resolve this issue.

Something like
amount = grp.Sum(x => Convert.ToDouble(x["AMOUNT"] == DBNull.Value ? 0 : x["AMOUNT"]));
If that is the line that is giving you the problem.

The way to find the number of CELLS with DBNulls for a specific column:
int numOfEmptyColA = MyDataTable.AsEnumerable().Where(p=>p.IsNull("ColA")).Count();

This:
amount = grp.Sum(x => Convert.ToDouble(x["AMOUNT"]))
will not work as you expect. If x["AMOUNT"] is DBNull.Value instead of a valid double, the conversion will fail with an exception. Instead, try:
amount = grp.Sum(x.Field<double?>("AMOUNT"))
if you expect that field to be a double. Sum will treat the null values as zero, per MSDN.

I'm not sure which one is getting the error, but you can can compare it to DBNull.Value like so.
String sCurr = obj.currency == DBNull.Value ? "" : obj.currency;

LINQ: Add RowNumber Column

How can the query below be modified to include a column for row number (ie: one-based index of results)?
var myResult = from currRow in someTable
where currRow.someCategory == someCategoryValue
orderby currRow.createdDate descending
select currRow;
EDIT1: I'm looking for the results to be {idx, col1, col2...col-n} not {idx, row}.
EDIT2: The row number should correspond to result rows not the table rows.
EDIT3: I DataBind these results to a GridView. My goal was to add a row number column to the GridView. Perhaps a different approach would be better.

Use the method-syntax where Enumerable.Select has an overload with the index:
var myResult = someTable.Select((r, i) => new { Row = r, Index = i })
.Where(x => x.Row.someCategory == someCategoryValue)
.OrderByDescending(x => x.Row.createdDate);
Note that this approach presumes that you want the original index of the row in the table and not in the filtered result since i select the index before i filter with Where.
EDIT: I'm looking for the results to be {idx, col1, col2...col-n} not
{idx, row}. The row number should correspond to result rows not
the table rows.
Then select the anonymous type with all columns you need:
var myResult = someTable.Where(r => r.someCategory == someCategoryValue)
.OrderByDescending(r => r.createdDate)
.Select((r, i) => new { idx = i, col1 = r.col1, col2 = r.col2, ...col-n = r.ColN });

Use this Select method:
Projects each element of a sequence into a new form by incorporating the element's index.
Example:
var myResult = someTable.Where(currRow => currRow.someCategory == someCategoryValue)
.OrderByDescending(currRow => currRow.createdDate)
.Select((currRow, index) => new {Row = currRow, Index = index + 1});
In response to your edit:
If you want a DataTable as result, you can go the non-Linq way by simply using a DataView and add a additional column afterwards.
someTable.DefaultView.RowFilter = String.Format("someCategory = '{0}'", someCategoryValue);
someTable.DefaultView.Sort = "createdDate";
var resultTable = someTable.DefaultView.ToTable();
resultTable.Columns.Add("Number", typeof(int));
int i = 0;
foreach (DataRow row in resultTable.Rows)
row["Number"] = ++i;

what about?
int i;
var myResult = from currRow in someTable
where currRow.someCategory == someCategoryValue
orderby currRow.createdDate descending
select new {Record = i++, currRow};

Just for fun, here's an alternative to Select with two arguments:
var resultsWithIndexes = myResult.Zip(Enumerable.Range(1, int.MaxValue - 1),
(o, i) => new { Index = i, Result = o });

According to you edit 1. NO, YOU CAN'T Linq returns the table as it is. You can build each column, but you lose the power of mapped entities.
This has been asked multiple times before: How do you add an index field to Linq results

There is no straightforward way if want to keep a flat list of columns (i.e. OP's Edit2) and also want a generic solution that works with any IEnumerable without requiring you to list out the set of expected columns.
However, there is a roundabout way to kinda go about it which is to dump the query results into a DataTable using the ToDataTable() method from here and then add a RowNumber column to that table.
var table = query.ToList().ToDataTable();
table.Columns.Add("RowNum", typeof(int));
int i = 0;
foreach (DataRow row in table.Rows)
row["RowNum"] = ++i;
This would likely cause performance issues with large datasets but it's not insanely slow either. On my machine a dataset with ~6500 rows took 33ms to process.
If your original query returned an anonymous type, then that type definition will get lost in the conversion so you'll lose the static typing on the column names of the resulting IEnumerable when you call table.AsEnumerable(). In other words, instead of being able to write something like table.AsEnumerable().First().RowNum you instead have to write table.AsEnumerable().First()["RowNum"]
However, if you don't care about performance and really want your static typing back, then you can use JSON.NET to convert the DataTable to a json string and then back to a list based on the anonymous type from the original query result. This method requires a placeholder RowNum field to be present in the original query results.
var query = (from currRow in someTable
where currRow.someCategory == someCategoryValue
orderby currRow.createdDate descending
select new { currRow.someCategory, currRow.createdDate, RowNum = -1 }).ToList();
var table = query.ToDataTable();
//Placeholder RowNum column has to already exist in query results
//So not adding a new column, but merely populating it
int i = 0;
foreach (DataRow row in table.Rows)
row["RowNum"] = ++i;
string json = JsonConvert.SerializeObject(table);
var staticallyTypedList = JsonConvert.DeserializeAnonymousType(json, query);
Console.WriteLine(staticallyTypedList.First().RowNum);
This added about 120ms to the processing time for my 6500 item dataset.
It's crazy, but it works.

I know I'm late to the party, but I wanted to show what worked for me.
I have a list of objects, and the object has an integer property on it for "row number"... or in this case, "Sequence Number". This is what I did to populate that field:
myListOfObjects = myListOfObjects.Select((o, i) => { o.SequenceNumber = i; return o; }).ToList();
I was surprised to see that this worked.

This one helped me in my case - Excel sheet extraction. anonymous type
var UploadItemList = ItemMaster.Worksheet().AsEnumerable().Select((x, index) => new
{
Code = x["Code"].Value == null ? "" : x["Code"].Value.ToString().Trim(),
Description = x["Description"].Value == null ? "" : x["Description"].Value.ToString().Trim(),
Unit = x["Unit"].Value == null ? "" : x["Unit"].Value.ToString().Trim(),
Quantity = x["Quantity"].Value == null ? "" : x["Quantity"].Value.ToString().Trim(),
Rate = x["Rate"].Value == null ? "" : x["Rate"].Value.ToString().Trim(),
Amount = x["Amount"].Value == null ? "" : x["Amount"].Value.ToString().Trim(),
RowNumber = index+1
}).ToList();

int Lc = 1;
var Lst = LstItemGrid.GroupBy(item => item.CategoryName)
.Select(group => new { CategoryName = group.Key, Items = group.ToList() ,RowIndex= Lc++ })
.ToList();

Copying data from var to DataTable after LINQ query

I am using LINQ query to filter data from a datatable and placing the data in to another datatable. For this I am using foreach statement to copy values from var to datatable. The datatable will be containing a very huge no. of rows so can you suggest me a way in which I can do the copying in a single go?
var drdatedisp = from row in dtfullreport.AsEnumerable()
group row by row.Field<string>("Order_Date") into g
select new
{
Order_Date = g.Key,
totalQnty = g.Sum(a => a.Field<int>("Item_Quantity")),
totalTax = g.Sum(a => float.Parse(a.Field<decimal>("TAXAMT").ToString())),
totalAmt = g.Sum(a => float.Parse(a.Field<decimal>("VALAMT").ToString()))
};
DataTable dtdatedisp = new DataTable();
dtdatedisp.Columns.Add("Order_Date");
dtdatedisp.Columns.Add("Item_Quantity");
dtdatedisp.Columns.Add("TAXAMT");
dtdatedisp.Columns.Add("VALAMT");
dtdatedisp.Rows.Clear();
foreach (var g in drdatedisp)
{
DataRow newRow1 = dtdatedisp.NewRow();
newRow1[0] = g.Order_Date;
newRow1[1] = g.totalQnty;
newRow1[2] = String.Format("{0:0.00}", g.totalTax);
newRow1[3] = String.Format("{0:0.00}", g.totalAmt);
dtdatedisp.Rows.Add(newRow1);
}
}
please see that there will be very less no of iterations....
is there any way ?? Can you Help me ??

There is a extension method called CopyToDataTable which is unfortunately on IEnumerable Data Row object. But with the use of following link, you can create/copy same extension method which will be called on any IEnumerable object And this would match your requirement.
Here is the link
With this you can directly write something like this in your code
drdatedisp.CopyToDataTable();

use CopyToDataTable(); Verified the result:
var results = (from myRow in myData.AsEnumerable()
where myRow.Field<double>("Num1") == 1
select myRow).CopyToDataTable();
DataTable dtTemp = (DataTable)results;
gvMain.DataSource = dtTemp;

c# LINQ to dataset IN clause contains, group, min

I am new to LINQ but am trying to tackle a tough one right off the bat. I am trying to do LINQ to dataset and emulate the following query...
SELECT smID, MIN(entID) FROM table
WHERE exID = :exID
AND smID IN (1,2,3,4,5,6,7,8, etc)
GROUP BY smID
The code I have so far is as follows...
DataTable dt = ds.Tables["myTable"];
var query =
from g in dt.AsEnumerable()
where g.Field<string>("exID") == exID
&& smIDs.Contains(g.Field<string>("smID"))
group g by g.Field<string>("smID") into rowGroup
select new
{
smID = rowGroup.Key,
minEntID = rowGroup.Min(g => g.Field<int>("entID"))
};
exID is a string variable in the method and smIDs is a List of strings also created earlier in the method. I created the following code to try and see my results and it throws an "System.InvalidCastException" error at query.Count...
if (query.Count() > 0)
{
foreach (var item in query)
{
string s = item.smID;
int i = (int)item.minEntID;
}
}
I have been unable to figure out what I am doing wrong.
VS points to...
minEntID = rowGroup.Min(g => g.Field<int>("entID"))
This is the first two lines of the stack trace...
at System.Data.DataRowExtensions.UnboxT`1.ValueField(Object value)
at System.Data.DataRowExtensions.Field[T](DataRow row, String columnName)
Any pointers would be most appreciated. Thanks.

Judging by the exception and stack trace, the type you're specifying for the endID field in your query doesn't match the DataType for that column in the DataTable. These must match -- you cannot use the Field method to cast the value to a different type.

I used Linqer to come up with this code:
from t in db.Table // your C# table / collection here, of course
where t.ExId == stackoverflow.ExId
&& (new int[] {1, 2, 3 }).Contains(t.SmId)
group t by new { t.SmId } into g
select new {
SmId = g.Key.SmId,
minEntID = g.Min(p => p.EntId)
}