How do i set DataRow class to last row of a Sql table

[pugalenthi]

I have to add a value to an empty field in the last row of the table using C#.

What changes should i make to the following code so that i can set 'thisRow' to last row in the table rather than to a new row.

DataRow thisRow = thisDataSet.Tab les["Table"].NewRow();
thisRow["Exit_time"] = Exittime;
thisDataSet.Tab les["Table"].Rows.Add(thisR ow);

[Plater]

Rows contain data. If they don't, they aren't real.
A "blank row" at the end of the table is just a template for filling in a new row.

Unluess you allow nulls in every column and create a row with nothing but nulls in it and don't have any auto-incrementing fields and no primary key.

[pugalenthi]

Rows contain data. If they don't, they aren't real.
A "blank row" at the end of the table is just a template for filling in a new row.

Unluess you allow nulls in every column and create a row with nothing but nulls in it and don't have any auto-incrementing fields and no primary key.

I guess you misunderstood what i said. In my table the last row has data in every column except for 1 column, which allows null. And now i need to insert value into this column in the last row. The value of this column will be a output of the c# program.

[Plater]

Scracth that.
You want to enter the data into the last row of a datatable in code?

You should be able to do this?

int lastrowidx=thisDataSet.Tables["Table"].Rows.Count-1;
DataRow thisRow = thisDataSet.Tables["Table"].Rows[lastrowidx];
thisRow["Exit_time"] = Exittime;

[pugalenthi]

Scracth that.
You want to enter the data into the last row of a datatable in code?

You should be able to do this?

int lastrowidx=thisDataSet.Tables["Table"].Rows.Count-1;
DataRow thisRow = thisDataSet.Tables["Table"].Rows[lastrowidx];
thisRow["Exit_time"] = Exittime;

I tried the above code in my program, and finally used the following lines,

thisDataSet.Tab les["Table"].Rows.Add(thisR ow);
thisAdapter.Upd ate(thisDataSet , "Table");

while i executed the code i got two exception,

System.Argument Exception occured in System.Data.dll
System.Reflecti on.TargetInvoca tionException occured in mscorlib.dll

I was not able to update the column of last row with the output of my program.

[Plater]

Oh, I thought the Row was already IN the DataTable.

What part is triggering the argument exception?

[pugalenthi]

Oh, I thought the Row was already IN the DataTable.

What part is triggering the argument exception?

int lastrowidx=this DataSet.Tables["Table"].Rows.Count-1;
DataRow thisRow = thisDataSet.Tab les["Table"].Rows[lastrowidx];
thisRow["Exit_time"] = Exittime;
thisDataSet.Tab les["Table"].Rows.Add(thisR ow);
thisAdapter.Upd ate(thisDataSet , "Table");

The first 3 lines of the code working perfectly fine. The variable Exittime's value gets passed to thisRow["Exit_time"]. I guess the problem is in the last two lines.

I need to just insert value into one column of the last row, whose other columns are already filled.

[Plater]

Is there a column with that name in the datatable?

[pugalenthi]

Is there a column with that name in the datatable?

Yes there is a column named Exit_time.

[Plater]

I take it that it's sqldatatype is that of "datetime" is the "exittime" variable you're trying to set it also a datetime object?


And to make sure we're on the same page:
int lastrowidx=this DataSet.Tables["Table"].Rows.Count-1;
DataRow thisRow = thisDataSet.Tab les["Table"].Rows[lastrowidx];
If you've done the above, I believe this line here will error:
thisDataSet.Tab les["Table"].Rows.Add(thisR ow);


You are in fact using the code you created and not mine (like above)?

[pugalenthi]

I take it that it's sqldatatype is that of "datetime" is the "exittime" variable you're trying to set it also a datetime object?


And to make sure we're on the same page:
int lastrowidx=this DataSet.Tables["Table"].Rows.Count-1;
DataRow thisRow = thisDataSet.Tab les["Table"].Rows[lastrowidx];
If you've done the above, I believe this line here will error:
thisDataSet.Tab les["Table"].Rows.Add(thisR ow);


You are in fact using the code you created and not mine (like above)?

I have set datatype to datetime in the database.

I dont get any error, i just get those 2 exceptions i have specified before.

I was able to enter into the database values for other columns during another event. During that event i used the following code to insert data into new row,

DataRow thisRow = thisDataSet.Tab les["Table"].NewRow();

The only difference i face in this event handler is that i need to insert data into 1 column of the last row.

[Plater]

DataRow thisRow = thisDataSet.Tab les["Table"].NewRow();
Creates a NEW row, and then you add it into the datatable with
this.DataSet.Ta bles["Table"].Rows.Add(thisR ow);

That's fine.

I was saying that if you pick a row already in the datatable and try to add it again, it will error.


You already have this:
idx | col1 | col2 | col3 | exittime
---------------------------------------------------
1 | data | data | data | (empty)
2 | data | data | data | (empty)
3 | data | data | data | (empty)
4 | data | data | data | (empty)

And you would just want to go to row 4(the last row) and add the datetime to the exittime column:
idx | col1 | col2 | col3 | exittime
---------------------------------------------------
1 | data | data | data | (empty)
2 | data | data | data | (empty)
3 | data | data | data | (empty)
4 | data | data | data | (a datetime that you specify)

right?

[pugalenthi]

DataRow thisRow = thisDataSet.Tab les["Table"].NewRow();
Creates a NEW row, and then you add it into the datatable with
this.DataSet.Ta bles["Table"].Rows.Add(thisR ow);

That's fine.

I was saying that if you pick a row already in the datatable and try to add it again, it will error.


You already have this:
idx | col1 | col2 | col3 | exittime
---------------------------------------------------
1 | data | data | data | (empty)
2 | data | data | data | (empty)
3 | data | data | data | (empty)
4 | data | data | data | (empty)

And you would just want to go to row 4(the last row) and add the datetime to the exittime column:
idx | col1 | col2 | col3 | exittime
---------------------------------------------------
1 | data | data | data | (empty)
2 | data | data | data | (empty)
3 | data | data | data | (empty)
4 | data | data | data | (a datetime that you specify)

right?

Yes, i want to do exactly the same.

[Plater]

Yes, i want to do exactly the same.

If the row is already IN the table, you do NOT want to use .NewRow()

Which is why I gave you this:

int lastrowidx=thisDataSet.Tables["Table"].Rows.Count-1;//the index of the last row in the table
DataRow thisRow = thisDataSet.Tables["Table"].Rows[lastrowidx];//the last row in the table
thisRow["Exit_time"] = Exittime;//set the Exit_time column to the DateTime object "Exittime"

[pugalenthi]

If the row is already IN the table, you do NOT want to use .NewRow()

Which is why I gave you this:

int lastrowidx=thisDataSet.Tables["Table"].Rows.Count-1;//the index of the last row in the table
DataRow thisRow = thisDataSet.Tables["Table"].Rows[lastrowidx];//the last row in the table
thisRow["Exit_time"] = Exittime;//set the Exit_time column to the DateTime object "Exittime"

I didnt use NewRow(). I used Row.Count-1 as specified in your code. Only on another occasion i used NewRow(), were i wanted to enter data in a new row.