DataTableReader.IsDBNull(Int32) Method
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Gets a value that indicates whether the column contains non-existent or missing values.
public:
override bool IsDBNull(int ordinal);
public override bool IsDBNull(int ordinal);
override this.IsDBNull : int -> bool
Public Overrides Function IsDBNull (ordinal As Integer) As Boolean
- ordinal
- Int32
The zero-based column ordinal.
true
if the specified column value is equivalent to DBNull; otherwise, false
.
The index passed was outside the range of 0 to FieldCount - 1.
An attempt was made to retrieve data from a deleted row.
An attempt was made to read or access a column in a closed DataTableReader .
The following example displays the contents of the column numbered 2 within the passed-in DataTableReader. If the value the column within a particular row is null, the code displays the text <NULL>. If the data within the column of the correct type, the example displays an error message for each row.
private static void PrintColumn(DataTableReader reader)
{
// Loop through all the rows in the DataTableReader
while (reader.Read())
{
if (reader.IsDBNull(2))
{
Console.Write("<NULL>");
}
else
{
try
{
Console.Write(reader.GetString(2));
}
catch (InvalidCastException)
{
Console.Write("Invalid data type.");
}
}
Console.WriteLine();
}
}
Private Sub PrintColumn(ByVal reader As DataTableReader)
' Loop through all the rows in the DataTableReader
While reader.Read()
If reader.IsDBNull(2) Then
Console.Write("<NULL>")
Else
Try
Console.Write(reader.GetString(2))
Catch ex As InvalidCastException
Console.Write("Invalid data type.")
End Try
End If
Console.WriteLine()
End While
End Sub
Call this method to see if there are null column values before calling the typed get methods (for example, GetByte, GetChar, and so on) to avoid raising an error.
Product | Versions |
---|---|
.NET | Core 2.0, Core 2.1, Core 2.2, Core 3.0, Core 3.1, 5, 6, 7, 8, 9 |
.NET Framework | 2.0, 3.0, 3.5, 4.0, 4.5, 4.5.1, 4.5.2, 4.6, 4.6.1, 4.6.2, 4.7, 4.7.1, 4.7.2, 4.8, 4.8.1 |
.NET Standard | 2.0, 2.1 |
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