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Get column name by value of field in datarow

My question is actually more about optimizing something I already have working.
I'm having a hard time believing there isn't a better way to do this with a LINQ query or lambda expression, so I thought I'd try here.
Each of my datatable rows has an item number and 43 quantity columns, that each correspond with a specific day. What I'm trying to do is take each row, and find the first quantity column that is greater than 0 and return that column name. My solution does work, but I'd really like to make it more efficient:
foreach (DataRow r in dt.Rows)
{
for (int i = 3; i <= dt.Columns.Count - 1; i++)
{
tempCol = dt.Columns(i).ColumnName.ToString();
rowValue = Convert.ToInt32(r(tempCol));
if (rowValue > 0)
{
tempCol = tempCol.Replace("Apat", "");
break;
}
}
var FirstAvailableDate = WorkDate.AddDays((dec)tempCol).ToShortDateString;
//use data in someway
}
Thanks for any suggestions ahead of time!!

the current code, each row * each column
get name of column
store it in variable
in match case perform String.Replace
my suggestion:
var allCols = dt.Columns
.Cast<DataColumn>()
.Select(col => col.ColumnName.Replace("Apat", ""))
.ToArray();
foreach (DataRow r in dt.Rows)
{
var firstCol =
r.ItemArray.Select((cell, position) => Tuple.Create(Convert.ToInt32(cell), position))
.FirstOrDefault(tuple => tuple.Item1 > 0);
if(firstCol == null) continue;
var colName = allCols[firstCol.Item2];
var FirstAvailableDate = WorkDate.AddDays((dec)colName).ToShortDateString;
//use data in someway
}

Please change following code
Tuple.Create(Convert.ToInt32(position), cell)
var colName = allCols[firstCol.Item1];
Working fine...!!!

How to add value to a value of certain clolumn and row in datatable C#

I have two datatables:
1.dtEmployee:
|agent_id|agent_name|sum|
2.dtReport:
|sale_date|agent_id|sum |
------------------------
For each record in dtReport I need to find agent_id in dtEmployee and add the value of dtReport["sum"] to dtEmployee["sum"]:
foreach (DataRow r in dtReport)
{
DataRow empRow = dtEmployee.find(dtReport["agent_id"]);
empRow["sum"] += r["sum"];
}
Is there a way that would allow me to accomplish this?

Something like this works:
private void AddValue(string agent_id, decimal sum)
{
DataRow[] row= dtEmployee.Select("agent_id= '"+agent_id+"'");
//since only one record with this agent_id, we take first record of array -> row[0]
decimal dSum= Convert.ToDecimal(row[0][column]);
dSum+= sum;
row[0]["sum"] = dSum;
}
and insert this function into loop:
foreach (DataRow r in dtReport)
{
AddValue(r["agent_id"], r["sum"]);
}

This can be achieved in many ways.
Option 1 :
foreach(DataRow row in dtEmployee.Rows)
{
var update = dtReport.AsEnumerable().FirstOrDefault(r => r.Field<string>("agent_id") == row.Field<string>("agent_id"));
if(update !=null)
row.SetField<float>("sum", update.Field<float>("sum"));
}
Option 2
Another option would be creating new table by joining DataTables
var results = from t1 in dtEmployee.AsEnumerable()
join t2 in dtReport.AsEnumerable()
on t1.Field<int>("agent_id") equals t2.Field<int>("agent_id")
select new { t1, t2 };
// Now we can construct new DataTable
DataTable result = new DataTable() ;
result.Columns.Add("agent_id", typeof(System.Int32));
result.Columns.Add("Name", typeof(System.String));
result.Columns.Add("sum", typeof(float));
foreach(var dr in results )
{
DataRow newRow = results.NewRow();
newRow["agent_id"] = dr.t1.Field<int>("agent_id");
newRow["agent_name"] = dr.t1.Field<string>("agent_name");
newRow["sum"] = dr.t2.Field<float>("sum");
// When all columns have been filled in then add the row to the table
results.Rows.Add(newRow);
}
Working sample
Hope this helps !

You could try something like this. Given that your agent_id and sum are integer.
foreach (DataRow r in dtReport.Rows)
{
dtEmployee.Select(string.Format("agent_id = {0}", r["agent_id"])).ToList<DataRow>().ForEach(
v => { v["sum"] = (v.IsNull("sum") ? 0 : v.Field<int>("sum")) + (r.IsNull("sum") ? 0 : r.Field<int>("sum")); });
}
Or equivalent code
foreach (DataRow r in dtReport.Rows)
{
DataRow[] empRow = dtEmployee.Select("agent_id = " + r["agent_id"]);
for (int i = 0; i < empRow.Length; i++)
{
empRow[i]["sum"] = (empRow[i].IsNull("sum") ? 0 : (int)empRow[i]["sum"]) + (r.IsNull("sum") ? 0 : (int)r["sum"]);
}
}

How to check duplicate rows in dataset?

I have a dataset which has duplicate rows i want my error message to execute when duplicate rows are present.
Below is my code please help
DataSet dsXml = new DataSet();
dsXml.ReadXml(new XmlTextReader(new StringReader(xml)));
Hashtable hTable = new Hashtable();
ArrayList duplicateList = new ArrayList();
foreach (DataRow drow in dsXml.Tables[0].Rows)
{
if (hTable.Contains(drow))
{
duplicateList.Add(drow);
}
else
{
script.Append("alert('Error - There are some Duplicate entries.'); ");
ErrorOcc = true;
if (ErrorOcc)
{
this.ScriptOutput = script + " ValidateBeforeSaving = false;";
this.StayContent = "yes";
return;
}
}
}

Your code is not working, because DataRow instances will be compared by references instead of comparing their fields. You can use custom comparer:
public class CustomDataRowComparer : IEqualityComparer<DataRow>
{
public bool Equals(DataRow x, DataRow y)
{
if (x.ItemArray.Length != y.ItemArray.Length)
return false;
for (int i = 0; i < x.ItemArray.Length; i++)
if (!x[i].Equals(y[i]))
return false;
return true;
}
public int GetHashCode(DataRow obj)
{
int hash = 17;
foreach (object field in obj.ItemArray)
hash = hash * 19 + field.GetHashCode();
return hash;
}
}
or use existing DataRowComparer which compares DataRow objects for equivalence by using value-based comparison:
HashSet<DataRow> set = new HashSet<DataRow>(DataRowComparer.Default);
// or: new HashSet<DataRow>(new CustomDataRowComparer());
foreach (DataRow row in dsXml.Tables[0].Rows)
{
if (!set.Add(row))
// duplicate row
}
You can also check if duplicated rows exist with Linq to DataSet query:
var duplicatedRowsExist = dsXml.Tables[0].AsEnumerable()
.GroupBy(r => r, DataRowComparer.Default)
.Any(g => g.Count() > 1);

You have to compare the content of the rows, not the rows themselves. Something like this should do it:
var hasDupes = dsXml.Tables[0].Rows
.AsEnumerable()
.GroupBy(row => new
{
row.Field<string>("Title"),
row.Field<string>("Address"),
row.Field<string>("State"),
row.Field<string>("City"),
row.Field<int>("Status"),
row.Field<int>("CreatedBy"),
row.Field<int>("UpdatedBy")
})
.Where(g => g.Count() > 1)
.Any();
if(hasDupes)
//Show error message

I think you have to alter you logic a little. You don't add the row to the hTable, so there are never duplicates. And I guess you have to show the message in the end, else the list will not be complete yet.
As stated by others, you do need Sergeys answer to get the comparison to work. If you have that covered, this code will solve the other logic problems.
foreach (DataRow drow in dsXml.Tables[0].Rows)
{
if (!hTable.Contains(drow))
{
hTable.Contains(drow);
hTable.Add(drow);
}
else
{
duplicateList.Add(drow);
}
}
script.Append("alert('Error - There are some Duplicate entries.'); ");
ErrorOcc = true;
if (ErrorOcc)
{
this.ScriptOutput = script + " ValidateBeforeSaving = false;";
this.StayContent = "yes";
return;
}

First, you need to define your comparison between rows. It appears when you create your hTable there is nothing in it, so the hTable.Contains call is always going to return false.
As a side note, you can't just compare a DataRow with another DataRow, it will use the default equality comparison (implemented using IEqualityComparer) and effectively boils down to a reference equality check, which none of the rows will be equal to each other.
Somewhere, you can either implement your own IEqualityCompariosn, or simply write a custom method to check the values of each row.

Here is the answer of my above Question
You can Check duplicate rows in dataset.. it is working fine try it.
DataSet dsXml = new DataSet();
dsXml.ReadXml(new XmlTextReader(new StringReader(xml)));
List<string> duplicateList = new List<string>();
foreach (DataRow drow in dsXml.Tables[0].Rows)
{
string strr = "";
for (int j = 0; j < dsXml.Tables[0].Columns.Count; j++ )
{
strr += drow[j];
}
if (!duplicateList.Contains(strr))
{
duplicateList.Add(strr);
}
else
{
script.Append("alert('Error - There are some Duplicate entries.'); ");
ErrorOcc = true;
if (ErrorOcc)
{
this.ScriptOutput = script + " ValidateBeforeSaving = false;";
this.StayContent = "yes";
return;
}
}
}

Update two columns in a DataTable using LINQ

I want to update two columns of DataTable in a single line using LINQ query. Currently I am using following two lines to do the same:
oldSP.Select(string.Format("[itemGuid] = '{0}'", itemGuid)).ToList<DataRow>().ForEach(r => r["startdate"] = stDate);
oldSP.Select(string.Format("[itemGuid] = '{0}'", itemGuid)).ToList<DataRow>().ForEach(r => r["enddate"] = enDate);
How can I do this in one line, using one Select?

You can do it in one 'line', just pass appropriate action delegate to ForEach method:
oldSP.Select(string.Format("[itemGuid] = '{0}'", itemGuid))
.ToList<DataRow>()
.ForEach(r => {
r["startdate"] = stDate;
r["enddate"] = enDate;
});
Also you can use LINQ to DataSet (looks more readable to me, than one-liner):
var rowsToUpdate =
oldSP.AsEnumerable().Where(r => r.Field<string>("itemGuid") == itemGuid);
foreach(var row in rowsToUpdate)
{
row.SetField("startdate", stDate);
row.SetField("enddate", enDate);
}

Use curly bracers to do two on more operations:
oldSP.Select(string.Format("[itemGuid] = '{0}'", itemGuid))
.ToList<DataRow>()
.ForEach(r => { r["enddate"] = enDate); r["startdate"] = stDate; });
But for code readability I would use old-fashioned foreach loop.

Try this :
oldSP.Select(string.Format("[itemGuid] = '{0}'", itemGuid)).ToList<DataRow>()
.ForEach(r => { r["startdate"] = stDate; r["enddate"] = enDate; });

I didn't like any of the examples I saw on the web, so here's my example
DataTable dt = new DataTable();
dt.Columns.Add("Year");
dt.Columns.Add("Month");
dt.Columns.Add("Views");
for (int year = 2011; year < 2015; year++)
{
for (int month = 1; month < 13; month++)
{
DataRow newRow = dt.NewRow();
newRow[0] = year;
newRow[1] = month;
newRow[2] = 0;
dt.Rows.Add(newRow);
}
}
dataGridView1.DataSource = dt;
//if using Lambda
//var test = dt.AsEnumerable().Where(x => x.Field<string>("Year") == "2013" && x.Field<string>("Month") == "2").ToList();
var test = (from x in dt.AsEnumerable()
where x.Field<string>("Year") == "2013"
where x.Field<string>("Month") == "2"
select x).ToList();
test[0][0] = "2015";
dt.AcceptChanges();
//if writing to sql use dt.SubmitChanges() instead

Find a string in all DataTable columns

I am trying to find a fast way to find a string in all datatable columns!
Followed is not working as I want to search within all columns value.
string str = "%whatever%";
foreach (DataRow row in dataTable.Rows)
foreach (DataColumn col in row.ItemArray)
if (row[col].ToString() == str) return true;

You can use LINQ. It wouldn't be any faster, because you still need to look at each cell in case the value is not there, but it will fit in a single line:
return dataTable
.Rows
.Cast<DataRow>()
.Any(r => r.ItemArray.Any(c => c.ToString().Contains("whatever")));
For searching for random text and returning an array of rows with at least one cell that has a case-insensitive match, use this:
var text = "whatever";
return dataTable
.Rows
.Cast<DataRow>()
.Where(r => r.ItemArray.Any(
c => c.ToString().IndexOf(text, StringComparison.OrdinalIgnoreCase) > 0
)).ToArray();

If you want to check every row of every column in your Datatable, try this (it works for me!).
DataTable YourTable = new DataTable();
// Fill your DataTable here with whatever you've got.
foreach (DataRow row in YourTable.Rows)
{
foreach (object item in row.ItemArray)
{
//Do what ya gotta do with that information here!
}
}
Don't forget to typecast object item to whatever you need (string, int etc).
I've stepped through with the debugger and it works a charm. I hope this helps, and good luck!

This can be achieved by filtering. Create a (re-usable) filtering string based on all the columns:
bool UseContains = false;
int colCount = MyDataTable.Columns.Count;
string likeStatement = (UseContains) ? " Like '%{0}%'" : " Like '{0}%'";
for (int i = 0; i < colCount; i++)
{
string colName = MyDataTable.Columns[i].ColumnName;
query.Append(string.Concat("Convert(", colName, ", 'System.String')", likeStatement));
if (i != colCount - 1)
query.Append(" OR ");
}
filterString = query.ToString();
Now you can get the rows where one of the columns matches your searchstring:
string currFilter = string.Format(filterString, searchText);
DataRow[] tmpRows = MyDataTable.Select(currFilter, somethingToOrderBy);

You can create a routine of search with an array of strings with the names of the columns, as well:
string[] elems = {"GUID", "CODE", "NAME", "DESCRIPTION"};//Names of the columns
foreach(string column in elems)
{
string expression = string.Format("{0} like '%{1}%'",column,
txtSearch.Text.Trim());//Search Expression
DataRow[] row = data.Select(expression);
if(row.Length > 0) {
// Some code here
} else {
// Other code here
}
}

You can get names of columns by using ColmunName Method. Then, you can search every column in DataTable by using them. For example, follwing code will work.
string str = "whatever";
foreach (DataRow row in dataTable.Rows)
{
foreach (DataColumn column in dataTable.Columns)
{
if (row[column.ColumnName.ToString()].ToString().Contains(str))
{
return true;
}
}
}

You can create a filter expression on the datatable as well. See this MSDN article. Use like in your filter expression.
string filterExp = "Status = 'Active'";
string sortExp = "City";
DataRow[] drarray;
drarray = dataSet1.Customers.Select(filterExp, sortExp, DataViewRowState.CurrentRows);
for (int i=0; i < drarray.Length; i++)
{
listBox1.Items.Add(drarray[i]["City"].ToString());
}