i have Dataset that contain any database.
how to run any query on this dataset ?
You could use a DataView:
var view = new DataView(dataSet.Tables("TableName"));
view.RowFilter = "ColumnName LIKE '%something%'"
foreach (var row in view.Rows)
{
// do something
}
or LINQ:
var results = from row in dataSet.Tables("Table").AsEnumerable()
where row.Field(Of String)("ColumnName").Contains("something")
select row;
foreach (var row in results)
{
// do something
}
Google should suffice for a question like this...
Hi I believe you can use Linq To Objects to query this dataset:
var results = (from r in mydatasetvar.AsQuarieable() .. )
See this for more info
Alternatively, you can loop through the tables, rows and columns of the dataset.
Related
I have a DataTable named dtEmployee with four columns, viz. EmployeeId, EmployeePosition, SupervisorPosition, SupervisorId which all are of type varchar(10).
I want to filter the results in dtEmployee whose result is equivalent to SQL Query below.
Select * from dtEmployee where EmployeePosition not in (Select distinct SupervisorPosition
from dtEmployee);
I have achieved the sub query equivalent by creating another DataTable named dtDistinctSupervisors as
dtDistinctSupervisors = dtEmployee.DefaultView.ToTable(true, "SupervisorPosNum");
This is equivalent to Select distinct SupervisorPosition
from dtEmployee
How can I get the whole query equivalent.
Your help is appreciated. Thanks.
Merin
Having Distinct inside an IN subquery makes no difference. This should dot it:
var dt = dtEmployee.AsEnumerable();
var result = dt.Where(emp => !dt.Any(sup =>
sup.Field<string>("SupervisorPosition") ==
emp.Field<string>("EmployeePosition")));
And to show the result in the Console:
foreach (DataRow row in result) // Loop over the rows.
{
Console.WriteLine("--- Row ---");
foreach (var item in row.ItemArray)
{
Console.Write("Item: ");
Console.WriteLine(item);
}
}
I have a DataTable(dataTable1) that have 25-30 columns. I want to bind a DataGridView by creating a small DataTable (dataTable2) that will have few columns (may 5-10) from the existing DataTable.
So my main task is to create a DataTable with fewer columns from the existing one.
Here is the code what I have tried so for..
DataTable subDataTable()
{
DataTable smallTable=new DataTable();
smallTable =dataTable1;// dataTable1 is already filled with data
smallTable.Columns.Remove("Column2");
smallTable.Columns.Remove("Column5");
smallTable.Columns.Remove("Column6");
smallTable.Columns.Remove("Column13");
smallTable.Columns.Remove("Column16");
return smallTable;
}
Its working fine. But I'm looking if there any better way.
You can try to convert your DataTable to IEnumerable,and Select necessary fields with linq like this:
var myValues = dataTable1.AsEnumerable()
.Select(x => new { col1 = x["Column1"], col2 = x["Column2"]..});
dataGridView.DataSource = myValues;
Your code will not work because you all you do is assign a variable smallTable with reference to dataTable1 and you removing columns from your original table object
Linq is faster to write but here is what you want to do to understand your issue:
DataTable smallTable = dataTable1.Clone(); // Copy data structure
// Now you can remove your columns
smallTable.Columns.Remove("Column2");
......
foreach (var row in dataTable1.Rows) // iterate all rows
{
var newRow = smallTable.NewRow();
foreach (var col in smallTable.Columns) // and iterate only needed columns
{
newRow[col.ColumnName] = row[col.ColumnName];
}
}
This is pretty much what sugar-coated by Linq
DataView dv = new DataView(dataTable1);
DataTable smallTable = dv.ToTable(true, new string[] { "Column2", "Column5"...});
https://social.msdn.microsoft.com/Forums/en-US/ac2c7c95-66d6-4db6-a6fb-4dccd5fa701e/is-there-a-better-way-to-get-subtable-with-selected-columns-of-a-datatable?forum=adodotnetdataset
Tomer.
I want to apply the follwing Sql query in my DataTable
SELECT MakeDistinct AS AfterDistinct
, COUNT(MakeDistinct) AS Count
FROM MyTable
GROUP BY MakeDistinct
Refer this Question for more details
something like:
var query = from row in table.AsEnumerable()
group row by row.Field<int>("MakeDistinct") into grp
select new {AfterDistinct = grp.Key, Count = grp.Count()};
foreach(var row in query) {
Console.WriteLine("{0}: {1}", row.AfterDistinct, row.Count);
}
Note that aggregating at the database server will usually be much more efficient than populating a DataTable over the network and then aggregating the DataTable.
You are partially looking for DataTable.Compute. That method can calculate aggregate functions for you. So you get something like:
object sumObject;
sumObject = myDataTable.Compute("Sum(Count)", ""); // second parameter is the where clause
For grouping by columns, see this question: Efficient DataTable Group By. It provides a Linq implementation as well as a 'non-Linq' implementation.
Use System.Data.DataSetExtensions and try something like this
var result = from row in dt.AsEnumerable()
group row by row.Field<int>("MakeDistinct") into grp
select new
{
MakeDistinct = grp.Key,
Count = grp.Count()
};
I have a DataSet with many DataTables each containing many columns plus a column buildingID.
I would like to filter the entire DataSet by giving it a value for buildingID. I would like the rows in every table with a buildingID of, say 343.
Is there any quick possible way in C#?
You can use DataTable.Select, which returns filtered rows from a DataTable matching a criteria.
foreach (DataTable table in dataset.Tables) {
var rows = table.Select("buildingID = " + buildingId.ToString());
// Do stuff with filtered rows
}
To easily get all the rows that match your criteria, here's a LINQ expression:
var rows = dataset.Tables.SelectMany(
t => t.Select("buildingID = " + buildingId.ToString()));
What about this?
var ds1 = new DataSet();
foreach (DataTable dt in ds1.Tables)
{
var filtereddt = dt.AsEnumerable().Where(row => row.Field<int>("buildingID") == 1).ToList();
//you can add these lists to another list array or something like that.
}
I want to delete a particular row from a DataTable named dt.
For a table in SQL, I could do something like:
DELETE FROM dt
WHERE BASELINE_FOLDER = baselineSubfolder
AND BASELINE_FILE = baselineFilename
AND BASELINE_CHECKSUM = baselineChecksum;
Is there an equivalent LINQ statement for this?
Assuming you don't have the model's and only a DataTable (this is what I understand from the OP).
//Cast to enumerable of `DataRow` and filter on your condition
var rows = dt.Rows.Cast<DataRow>().Where(row => row["BASELINE_FOLDER"] == baselineSubFolder && row["BASELINE_FILE" == baselineFilename
&& row["BASELINE_CHECKSUM"] == baselineChecksum).ToArray();
//Loop through and remove the rows that meet the condition
foreach(DataRow dr in rows)
{
dt.Rows.Remove(dr);
}
you can convert the data table to list and can use RemoveAt() to do so.
You can convert it to list and use the below code
string baseLineFolder=dt.Rows["BASELINE_FOLDER"].ToString();
string baseLineFile=dt.Rows["BASELINE_FILE"].ToString();
string baseLineChecksum=dt.Rows["BASELINE_CHECKSUM"].ToString();
var dtresult = dt.AsEnumerable();
var result=(from r in dtresult
where(r.Field<string>("BASELINE_FOLDER")!=baseLineFolder)
&&(r.Field<string>("BASELINE_FILE")!=baseLineFile)
&&(r.Field<string>("BASELINE_CHECKSUM ")!=baseLineChecksum)
select r).ToList();