How to find whether record exist before write again

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I am trying to convert text file, read the text file and loaded
them to variables.

now I want to see whether record exist before write again

Is this correct way see record exit
DataRow[] foundRows;
foundRows = this.timeattDataSet.Tables["Data"].Select("Token_no= @cToken and Date = @datetime and Time = @cTime");

Ajith

(I am new to c#)

What I have tried:

Token1 = str.ToString().Substring(0, 9).Trim();
cToken2 = '5' + cToken1.PadLeft(5, '0');
cToken = cToken2.Substring(0, 6);
cDate = str.ToString().Substring(10, 10);
cTime = str.ToString().Substring(21, 2) + str.ToString().Substring(24, 2);
cIdno = str.ToString().Substring(30, 1);
datetime = Convert.ToDateTime(cDate);

DataRow[] foundRows;
foundRows = this.timeattDataSet.Tables["Data"].Select("Token_no= @cToken and Date = @datetime and Time = @cTime");

Posted 11-May-17 1:43am

Member 12931315

Updated 11-May-17 2:08am

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Comments

Michael_Davies 11-May-17 8:13am

You have to construct your Select SQL with the data for the parameters embedded, your existing query uses parameter names (@cToken etc.) and there is no way of passing the values for the parameters to a Table.Select. This is okay for a table in memory as it is not prone to SQL injection, never to be used for queries to SQL server by command.

Example;

.Select("Token_no='"+ cToken +"' and Date = ...etc.

Note: as above you will also have to enclose the parameter data in single quotes for string fields.

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Richard Deeming · Accepted Answer · 2017-05-11T02:08:00

Solution 1

Use LINQ:

C#

bool rowExists = timeattDataSet.Tables["Data"].AsEnumerable()
    .Any(row => string.Equals(row.Field<string>("Token_no"), cToken, StringComparison.OrdinalIgnoreCase) && row.Field<DateTime>("Date") == datetime);

Posted 11-May-17 2:08am

Richard Deeming

Comments

Member 12931315 11-May-17 8:50am

Hi Richard
Thank you very much Richard it's working
only problem is it enable to write several record in while loop and
give break error any idea why is that ?

Thanks again

Ajith

Richard Deeming 11-May-17 9:03am

What's the error?

Member 12931315 11-May-17 9:07am

Managed Debugging Assistant 'ContextSwitchDeadlock' : 'The CLR has been unable to transition from COM context 0x1801160 to COM context 0x18010a8 for 60 seconds. The thread that owns the destination context/apartment is most likely either doing a non pumping wait or processing a very long running operation without pumping Windows messages. This situation generally has a negative performance impact and may even lead to the application becoming non responsive or memory usage accumulating continually over time. To avoid this problem, all single threaded apartment (STA) threads should use pumping wait primitives (such as CoWaitForMultipleHandles) and routinely pump messages during long running operations.'

Richard Deeming 11-May-17 9:08am

That error doesn't seem to be associated with the code you've posted.

Member 12931315 11-May-17 9:13am

Hihope error list is not that long.
without checking row exist I can write over 30000 records
with check only 109 records written and break

Thanks in advance

Ajith

Member 12931315 11-May-17 9:17am

while! null

foundRows = this.timeattDataSet.Tables["Data"].Select("Token_no= @cToken and Date = @datetime and Time = @cTime");

if foundRows == false
'write to data file'

Member 12931315 11-May-17 9:28am

Now I found It application in break mode, there is option asking to continue
I click and It's working, Is it a visual studio problem ?

Ajith

Richard Deeming 11-May-17 13:02pm

Yes, it's probably just Visual Studio warning you that your code is taking a long time.