How can you tell if a column exists?

[Glowworm27]

Hello all

I have a dataset, and I need to know if a Column(field) exists in the dataset before I try to get data from it.

If dsMyDataset.tables(0).Rows(0).Item("estNum") <> 0 Then
   bIsBFRCREcord = True
End if

I get an error that column "estnum" does not exists in the dataset.

I dont want the user to get an error if they don't have that column in thier database.

George Oakes
Check out this awsome .Net Resource!

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[BoulderBum]

If ds.Tables(0).Rows(0)("estNum") <> Null Then

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[Glowworm27]

BoulderBum,

Nice try, but that will NOT work.

First in ASP.net you cannot use Null, it is no longer used.

You must write the if statement this way.

 If IsDBNull(.Rows(0)("estNum")) Then
   ' Do something
 End if

Secondly this will still throw the same error: "Column estNum does not exists in Table"

what your statement does is check the value in the column, and because it doesn't exist in the table you get the error.

I need a way to check if the column exists first, so I can then check if it has a value after.

Thanks for trying

George Oakes
Check out this awsome .Net Resource!

http://www.learnvisualstudio.net?referedby=54275&cam=Tek-Tips

 

[chiph]

What about this:

If ds.Tables(0).Columns.Contains("estNum") Then

Chip H.


____________________________________________________________________
If you want to get the best response to a question, please read FAQ222-2244 first

 

[ashstampede]

this should work

if ds.tables(0).columns("estnum") = true then
    bIsBFRCREcord = True
end if

or cast your dataset to a datatable and then you could do

dim dt as datatable = new datatable
dt = ds.tables(0)
if dt.Columns("estnum") = true then
 'do your stuff
end if

 

[BoulderBum]

First in ASP.net you cannot use Null, it is no longer used."

Actually "null" is used in C# (my primary language). I just forgot the VB.NET translation:

If ds.Tables(0).Rows(0)("estNum") <> Null Then
-should have been-
If ds.Tables(0).Rows(0)("estNum") <> Nothing Then

In this case, you don't want to use DBNull because you're checking a row value, you're checking whether the column object reference is set to an instance.

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