I have DataTable with two columns Author and Bookname.
I want to check if the given string value Author already exists in the DataTable. Is there some built in method to check it, like for Arrays array.contains?
You can use LINQ-to-DataSet with Enumerable.Any:
String author = "John Grisham";
bool contains = tbl.AsEnumerable().Any(row => author == row.Field<String>("Author"));
Another approach is to use DataTable.Select:
DataRow[] foundAuthors = tbl.Select("Author = '" + searchAuthor + "'");
if(foundAuthors.Length != 0)
{
// do something...
}
Q: what if we do not know the columns Headers and we want to find if any
cell value PEPSI exist in any rows'c columns? I can loop it all to
find out but is there a better way? –
Yes, you can use this query:
DataColumn[] columns = tbl.Columns.Cast<DataColumn>().ToArray();
bool anyFieldContainsPepsi = tbl.AsEnumerable()
.Any(row => columns.Any(col => row[col].ToString() == "PEPSI"));
You can use Linq. Something like:
bool exists = dt.AsEnumerable().Where(c => c.Field<string>("Author").Equals("your lookup value")).Count() > 0;
DataRow rw = table.AsEnumerable().FirstOrDefault(tt => tt.Field<string>("Author") == "Name");
if (rw != null)
{
// row exists
}
add to your using clause :
using System.Linq;
and add :
System.Data.DataSetExtensions
to references.
You should be able to use the DataTable.Select() method. You can us it like this.
if(myDataTable.Select("Author = '" + AuthorName.Replace("'","''") + '").Length > 0)
...
The Select() funciton returns an array of DataRows for the results matching the where statement.
you could set the database as IEnumberable and use linq to check if the values exist.
check out this link
LINQ Query on Datatable to check if record exists
the example given is
var dataRowQuery= myDataTable.AsEnumerable().Where(row => ...
you could supplement where with any
Related
I wanted to search for multiple values from the same column using OR in linq. In SQL, it is something like this:
var query = "Select * from table where id = 1";
query += "OR where id = 2";
The id is from an array of ids so i pass the id to a variable and loop it. The number of id in the array is not fixed and depends on how many ids chosen by the user by checking on the checkbox in the table. Because if i do as below, it will return null because it somewhat inteprets my where query as AND. How do i change it so that it will get rows from all ids(using OR)?
Request request = db.Requests;
var selectedIdList = new List<string>(arrId);
if (arrId.Length > 0)
{
for (var item = 0; item <= selectedIdList.Count() - 1; item++)
{
var detailId = Convert.ToInt32(selectedIdList[item]);
request = request.Where(y => y.Id == detailId);
}
}
Simply use || for OR and && for AND inside Where
But I prefer :
request.Where(y => selectedIdList.Contains(y.Id));
If selectedIdList is an array of Strings :
request.Where(y => selectedIdList.Contains(y.Id.ToString());
You can use LinqKit. Linqkit provides things to create predicate dynamically
Just install linqKit using packageManager, And use predicateBuilder to build predicate
var predicate = PredicateBuilder.True<Patient>();
predicate=predicate.And(...)
OR
predicate=predicate.Or(...)
And then use predicate in ur where clause
This way you can create Or (dynamically) as you would in dynamic SQL
You can get more details from here
https://www.c-sharpcorner.com/UploadFile/c42694/dynamic-query-in-linq-using-predicate-builder/
I am very much new to the Linq queries. I have the set of records in the csv which is like below
ProdID,Name,Color,Availability
P01,Product1,Red,Yes
P02,Product2,Blue,Yes
P03,Product1,Yellow,No
P01,Product1,Red,Yes
P04,Product1,Black,Yes
I need to check for the Names of the each product and if its is not the same in all the records then I need to send an error message.I know the below query is used to find the duplicates in the records but not sure how can I modify it check if it all has the same values.
ProductsList.GroupBy(p => p.Name).Where(p => p.Count() > 1).SelectMany(x => x);
var first = myObjects.First();
bool allSame = myObjects.All(x=>x.Name == first.Name);
Enumerable.All() will return true if the lambda returns true for all elements of the collection. In this case we're checking that every object's Name property is equal to the first (and thus that they're all equal to each other; the transitive property is great, innit?). You can one-line this by inlining myObjects.First() but this will slow performance as First() will execute once for each object in the collection. You can also theoretically Skip() the first element as we know it's equal to itself.
if I understand correctly you want to check if product exists in the list
using System.Linq;
private bool ItemExists(string nameOfProduct) {
return ProductsList.Any(p=> p.Name== nameOfProduct);
}
UPD after author comment:
To know all the records that are not having the same name as the first record:
var firstName = ProductsList[0].Name;
var differentNames = ProductsList.Where(p => p.Name != firstName);
Another option (just to have all other names): ProductsList.Select(p => p.Name).Where(n => n != firstName).Distinct()
Old version
So, if there are at least two different names then you should return an error?
LINQ way: return ProductsList.Select(p => p.Name).Distinct().Count() <= 1
More optimizied way:
if (ProductsList.Count == 0)
return true;
var name = ProductsList[0].Name;
for (var i = 1; i < ProductsList.Count; i++)
{
if (ProductsList[i].Name != name)
return false;
}
return true;
I used .Net framwork 4.0 with WinForm application component DataGridView and set DataSource with DataTable.Then there's a button to add row into DataGridView.
That code like this.
gridTable = (DataTable)dgrMainGrid.DataSource;
DataRow dr = gridTable.NewRow();
Before adding New Row into DataTable I checked if there's a duplicate row.To do that I used this LINQ Query.
//Item Code cannot duplicate
var results = from itmCode in gridTable.AsEnumerable()
where (itmCode.Field<string>("Item Code") == txtGrdItmLoc.Text)
select itmCode;
There after how I check the duplicate rows available or not in the data table?
if(//doWhatever function here ){
//if there's duplicate row values
isNotDuplicate = false;
}
else{
isNotDuplicate=true;
}
Before go to following step I need to get is there a duplicate or not and set it into isNotDuplicate variable or similar thing to check that. so i think to count the results rows but there's no such function to count 'var results`, Any possibility to do that?
if (!isDuplicate)
{
dr["#"] = true;
dr["Item Code"] = lSysItemCode;
dr["Stock Code"] = txtGdrItmItemLoc.Text;
dr["Brand"] = txtGrdItmBrand.Text;
dr["Model No"] = cmbGrdItmModel.SelectedValue.ToString();
gridTable.Rows.Add(dr);
dgrMainGrid.DataSource = gridTable;
}
I can use for loop with DataTable and check whether it's contain new value that equals to "Item Code" but I looking alternative method with linq.
Simply I'm looking replacement for this by using linq.
foreach (DataRow r in gridTable.Rows) {
if (r["Item Code"].ToString() == txtGrdItmLoc.Text) {
isDuplicate = true;
}
}
Sample Project : http://1drv.ms/1K4JnHt
Sample Code : http://pastebin.com/v7NMdUrf
You have not made it clear that in your DataTable if you are looking for duplicates for any specific Item Code or for any Item Code. Anyways,here is the code for both the scenarios:-
If you are looking for duplicates for any specific Item Code then you can simply check the count like this:-
bool istxtGrdItmLocDuplicate = gridTable.AsEnumerable()
.Count(x => x.Field<string>("ItemCode") == txtGrdItmLoc.Text) > 1;
If you are looking for duplicates in the entire DataTable, then simply group by Item Code and check the respective count for each Item Code like this:-
bool isDuplicate = gridTable.AsEnumerable()
.GroupBy(x => x.Field<string>("ItemCode")
.Any(x => x.Count() > 1);
IEnumerable<T> has a Count() method (check here), if you are not seeing it in intellisense then you are missing some using instruction, like using System.Linq; or some other...
Then you would just do:
if(results.Count()>0){
//if there's duplicate row values
isNotDuplicate = false;
}
else
{
isNotDuplicate=true;
}
First cast it to IEnumerable :
Convert DataRowCollection to IEnumerable<T>
Then you can use LINQ extension methods to do something like this (to check all values that has duplicates):
var duplicates = resultsList.Where(r => resultsList.Count(r2 => r2.Field<string>("Item Code") == r.Field<string>("Item Code")) > 0);
If you want check each value for duplicate you can use .Count method, something like this:
bool hasDuplicates = resultsList.Count(r2 => r2.Field<string>("Item Code") == "your code") > 1;
Ok, if for some reason this doesn't work you can write this function yourself:
public static class Helper
{
// or other collection type
public static int MyCount<T>(this IEnumerable<T> collection, Func<T, bool> function)
{
int count = 0;
foreach (T i in collection)
if (function(i)) ++count;
return count;
}
}
And use it like :
results.MyCount(r => r.Field<string>("Item Code") == "Item Code");
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();
How can I check the results of LINQ query for a specific string value?
I have the following linq query:
IEnumerable<DataRow> rows = searchParamsTable.AsEnumerable()
.Where(r => r.Field<String>("TABLE") == tableNumbers[i].ToString()
&& r.Field<String>("FIELD ") == fieldName[i]);
I want to see if the result of that query contains a string(passed in form a text box) "wildcardSearchString".
var searchRows =
rows.Where(tr => tr.ItemArray
.Any(ti => ti.ToString().IndexOf("wildcardSearchString", StringComparison.CurrentCultureIgnoreCase) > 0))
This will go through each of the rows that was returned, and see if "wildcardSearchString" is in the rows item string representation (ignoring case). Here's the problem though, this won't get you wildcard search support, so you'll have to figure that one out yourself. You can try to use Regex, which would require a slight modification:
string searchPattern = "some*string".Replace("*", ".*");
var searchRows =
rows.Where(tr => tr.ItemArray
.Any(ti => Regex.IsMatch(ti.ToString(), searchPattern)))
Hope that helps. Just be warned that if they decide to try supplying a Regex pattern than this might really mess up whatever they were searching for, so you just need to be careful of input.
try with this code
DataRow[] array = rows.ToArray();
array.Contains(yourIndex, yourTextBox.Text);
Add this extension
public static bool Contains(this DataRow[] dataRows, string value, int index)
{
foreach(var row in dataRows)
{
if(row[index].ToString().Contains(value))
{
return true;
}
}
return false;
}
Boolean found = false;
foreach(Datarow d in rows)
{
foreach(object o in d.ItemArray)
{
if(o.ToString().Contains("test")
{
found=true;
break;
}
}
}
Do you mean something like this?
I don't know if you're aware of the built-in search capabilities of a DataTable? You could use its Select method:
DataRow[] rows = searchParamsTable
.Select("TABLE = 'Table1' AND FIELD like '%wildcardSearchString%'");
Linq is OK but not always required :).