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Bryan Anderson
Bryan Anderson

Reputation: 16129

How to find out if a column exists in a DataRow?

I am reading an XML file into a DataSet and need to get the data out of the DataSet. Since it is a user-editable config file the fields may or may not be there. To handle missing fields well I'd like to make sure each column in the DataRow exists and is not DBNull.

I already check for DBNull but I don't know how to make sure the column exists without having it throw an exception or using a function that loops over all the column names. What is the best method to do this?

Upvotes: 62

Views: 118639

Answers (4)

Alexander Abakumov
Alexander Abakumov

Reputation: 14539

Another way to find out if a column exists is to check for Nothing the value returned from the Columns collection indexer when passing the column name to it:

If dataRow.Table.Columns("ColumnName") IsNot Nothing Then
    MsgBox("YAY")
End If

This approach might be preferred over the one that uses the Contains("ColumnName") method when the following code will subsequently need to get that DataColumn for further usage. For example, you may want to know which type has a value stored in the column:

Dim column = DataRow.Table.Columns("ColumnName")
If column IsNot Nothing Then
    Dim type = column.DataType
End If

In this case this approach saves you a call to the Contains("ColumnName") at the same time making your code a bit cleaner.

Upvotes: 4

Phillip Wells
Phillip Wells

Reputation: 7622

You can use DataSet.Tables(0).Columns.Contains(name) to check whether the DataTable contains a column with a particular name.

Upvotes: 23

John Chuckran
John Chuckran

Reputation: 2389

DataRow's are nice in the way that they have their underlying table linked to them. With the underlying table you can verify that a specific row has a specific column in it.

    If DataRow.Table.Columns.Contains("column") Then
        MsgBox("YAY")
    End If

Upvotes: 186

Anders
Anders

Reputation: 12560

You can encapsulate your block of code with a try ... catch statement, and when you run your code, if the column doesn't exist it will throw an exception. You can then figure out what specific exception it throws and have it handle that specific exception in a different way if you so desire, such as returning "Column Not Found".

Upvotes: -3

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