I ran into a problem trying to remove a row from a datatable in C#. The problem is that the datatable is built from SQL, so it can have any number of columns and may or may not have a primary key. So, I can't remove a row based on a value in a certain column or on a primary key.
Here's the basic outline of what I'm doing:
//Set up a new datatable that is an exact copy of the datatable from the SQL table.
newData = data.Copy();
//...(do other things)
foreach (DataRow dr in data.Rows)
{
//...(do other things)
// Check if the row is already in a data copy log. If so, we don't want it in the new datatable.
if (_DataCopyLogMaintenance.ContainedInDataCopyLog(dr))
{
newData.Rows.Remove(dr);
}
}
But, that gives me an error message, "The given DataRow is not in the current DataRowCollection". Which doesn't make any sense, given that newData is a direct copy of data. Does anyone else have any suggestions? The MSDN site wasn't much help.
Thanks!
Your foreach needs to be on the copy, not the original set. You cannot remove an object contained in collection1 from collection2.
foreach (DataRow dr in newData.Rows)
Otherwise you could use a counter to remove at an index. Something like this:
for(int i = 0; i < data.Rows.Count; i++)
{
if (_DataCopyLogMaintenance.ContainedInDataCopyLog(data.Rows[i]))
{
newData.Rows.RemoveAt(i);
}
}
Related
First I have last update file from DB
DataTable excelData = ReadSCOOmega(lastUploadFile);
, after this iterate over this data
foreach (DataRow currentRow in rows)
{
currentRow.
}
Is that possible to change da data in the foreach loop.I can access only the value of this data
currentRow.Field<object>("Some column name")
but not to change it.My idea is selected.I have a multiple deals in excel file and when is upload to DB, I need to make changes in this file.Is that possible or I need to store the data in other collection?
You can do that like :
foreach (DataRow currentRow in excelData.Rows)
{
currentRow.BeginEdit();
currentRow["ColumnName"] = value;
//.....
currentRow.EndEdit();
}
You can use indexer to set the data stored to the field: currentRow["columnName"] = value.
See MSDN DataRow.Item Property
In following code i want read dataset records for only once to avoid database transaction and want to iterate loop in accordance with first row.
//InitializeConfig method return dataset which contains 6 records
// i.e. Table with 6 rows and 6 columns
dsConfig = objConfig.InitializeConfig(objConfig, NoOfGates);
foreach (DataRow dr in dsConfig.Tables[0].Rows)
{
objCR.GetCard(objConfig.iIndex, objConfig.iCRNo, out MainId);
}
but I am getting always records from first rows only for each iteration.
The question is rather unclear, but let me expand on the comment from venerik. It is pointless to iterate over rows when you're not using them inside the loop body.
foreach (DataRow dr in dsConfig.Tables[0].Rows)
{
// starting from here the variable dr is available
Console.WriteLine(dr["GateNo"].ToString()) // this should print the value of GateNo column for each row
objCR.GetCard(objConfig.iIndex, objConfig.iCRNo, out MainId);
}
Here No need to use Foreach loop simply I can Iterate for loop for my dataset Object
for(i=0; i<dsConfig.Rows.Count; i++)
{
objCR.GetCard(Convert.ToInt32(dsConfig.Tables[0].Rows[i].ItemArray[2]), Convert.ToInt32(dsConfig.Tables[0].Rows[i].ItemArray[3]), out MainId);
}
Because My iIndex and iCRNo parameters from dataset passed to GetCard Method.
I am iterating a DataTable in my C# code. I try to get the contents using of a column named "columnName" of row named "row" using -
object value = row["ColumnName"];
I get this error -
Error: System.Reflection.TargetInvocationException: Exception has been
thrown by the target of an invocation.
---> System.ArgumentException: Column 'FULL_COUNT' does not belong to table . at System.Data.DataRow.GetDataColumn(String columnName)
How is this possible ? My SQL query/result set has a column by that name and the query even runs in management studio.
How do I fix this error ?
I am guessing your code is iteration supposed to be something like this
DataTable table = new DataTable();
foreach (DataRow row in table.Rows) {
foreach (DataColumn col in table.Columns) {
object value = row[col.ColumnName];
}
}
If this is the case, row["ColumnName"] in each iteration looks for the same column with name ColumnName which obviously does not exists in your table.
The correct way is row[ColumnName] or row[col.ColumnName] in iteration above
I had a similar issue on my c# code, using a dataset which I had successfully initialized and populated with data from the DB.
So my return set was:
data = new Byte[0];
data = (Byte[])(dataset.Tables[0].Rows[0]["systemLogo_img"]);
Of course the error was in t finding the column 'systemLogo_img'.
I noted that you simply do NOT have to call /qualify the column name. So the correction is:
data = new Byte[0];
data = (Byte[])(dataset.Tables[0].Rows[0].ItemArray[0]);
Simply put: use "ItemArray" at position.
Thanks
Do not write Gridview column names instead of Database column names.
dataGridViewEmployeeClass.Rows[n].Cells[0].Value = item["write the Database Column names"].ToString();
Try this, make sure your column name is same
DataTable dt = new DataTable();
dt.Columns.Add("abc", typeof(string));
DataRow dr = dt.NewRow();
dr["abc"]="";
I had a similar issue which was very basic to fix.
I was querying with a specific column name rather than Select * (i.e. Select Title). Beginner's error but happens to everyone.
If you want to check if the column exists in the DataRow before accessing the value the following block can help...
if (dataRow.Table.Columns.Contains("theColumnName"))
{
// do work
string text = string.Empty;
if (dataRow["theColumnName"] != System.DBNull.Value)
{
text = Convert.ToString(dataRow["theColumnName"]);
}
}
If it doesn't exist and it needs to be added to the data table you can add the column using #Karthick Ganesan's example
// add a column
dataTable.Columns.Add("theColumnName", typeof(string));
I had same issue was trying to pass two different keys for same product.
item.Product = SqlHelper.GetSafeString(dr, "ProductName");
item.Product = SqlHelper.GetSafeString(dr, "Product");
I'm trying to append more values the rows of a DataTable. The original data read from database doesn't have two additional columns I'd like to add. I've got this so far -
myTable.Columns.Add("type", typeof(int));
myTable.Columns.Add("rate", typeof(int));
foreach (DataRow rows in myTable.Rows)
{
if (rows["dst"] == "1875")
{
//How to append values to this current row?
}
}
Please advice.
Here is the answer
foreach (DataRow rows in myTable.Rows)
{
if (rows["dst"] == "1875")
{
//How to append values to this current row?
rows["type"] = 32;
rows["rate"] = 64;
}
}
Also as a best practice - change rows in your for loop to row. It should be singular as it represents a single object - not a collection.
I have created a solution which read a large csv file currently 20-30 mb in size, I have tried to delete the duplicate rows based on certain column values that the user chooses at run time using the usual technique of finding duplicate rows but its so slow that it seems the program is not working at all.
What other technique can be applied to remove duplicate records from a csv file
Here's the code, definitely I am doing something wrong
DataTable dtCSV = ReadCsv(file, columns);
//columns is a list of string List column
DataTable dt=RemoveDuplicateRecords(dtCSV, columns);
private DataTable RemoveDuplicateRecords(DataTable dtCSV, List<string> columns)
{
DataView dv = dtCSV.DefaultView;
string RowFilter=string.Empty;
if(dt==null)
dt = dv.ToTable().Clone();
DataRow row = dtCSV.Rows[0];
foreach (DataRow row in dtCSV.Rows)
{
try
{
RowFilter = string.Empty;
foreach (string column in columns)
{
string col = column;
RowFilter += "[" + col + "]" + "='" + row[col].ToString().Replace("'","''") + "' and ";
}
RowFilter = RowFilter.Substring(0, RowFilter.Length - 4);
dv.RowFilter = RowFilter;
DataRow dr = dt.NewRow();
bool result = RowExists(dt, RowFilter);
if (!result)
{
dr.ItemArray = dv.ToTable().Rows[0].ItemArray;
dt.Rows.Add(dr);
}
}
catch (Exception ex)
{
}
}
return dt;
}
One way to do this would be to go through the table, building a HashSet<string> that contains the combined column values you're interested in. If you try to add a string that's already there, then you have a duplicate row. Something like:
HashSet<string> ScannedRecords = new HashSet<string>();
foreach (var row in dtCSV.Rows)
{
// Build a string that contains the combined column values
StringBuilder sb = new StringBuilder();
foreach (string col in columns)
{
sb.AppendFormat("[{0}={1}]", col, row[col].ToString());
}
// Try to add the string to the HashSet.
// If Add returns false, then there is a prior record with the same values
if (!ScannedRecords.Add(sb.ToString())
{
// This record is a duplicate.
}
}
That should be very fast.
If you've implemented your sorting routine as a couple of nested for or foreach loops, you could optimise it by sorting the data by the columns you wish to de-duplicate against, and simply compare each row to the last row you looked at.
Posting some code is a sure-fire way to get better answers though, without an idea of how you've implemented it anything you get will just be conjecture.
Have you tried Wrapping the rows in a class and using Linq?
Linq will give you options to get distinct values etc.
You're currently creating a string-defined filter condition for each and every row and then running that against the entire table - that is going to be slow.
Much better to take a Linq2Objects approach where you read each row in turn into an instance of a class and then use the Linq Distinct operator to select only unique objects (non-uniques will be thrown away).
The code would look something like:
from row in inputCSV.rows
select row.Distinct()
If you don't know the fields you're CSV file is going to have then you may have to modify this slightly - possibly using an object which reads the CSV cells into a List or Dictionary for each row.
For reading objects from file using Linq, this article by someone-or-other might help - http://www.developerfusion.com/article/84468/linq-to-log-files/
Based on the new code you've included in your question, I'll provide this second answer - I still prefer the first answer, but if you have to use DataTable and DataRows, then this second answer might help:
class DataRowEqualityComparer : IEqualityComparer<DataRow>
{
public bool Equals(DataRow x, DataRow y)
{
// perform cell-by-cell comparison here
return result;
}
public int GetHashCode(DataRow obj)
{
return base.GetHashCode();
}
}
// ...
var comparer = new DataRowEqualityComparer();
var filteredRows = from row in dtCSV.Rows
select row.Distinct(comparer);