24.1 Comments/Troubleshooting

The commonly used public properties of the DataColumn class are listed in Table 24-1.

Table 24-1. DataColumn properties

Property	Description
AllowDBNull	Gets or sets whether null values can be stored in the column.
AutoIncrement	Gets or sets whether the column automatically increments with each new row added to the table.
AutoIncrementSeed	Gets or sets the amount that an automatically incrementing column is incremented each time a row is added to the table.
AutoIncrementStep	Gets or sets the starting value for an automatically incrementing column.
Caption	Gets or sets the caption for the column used as the default value for the Caption property in controls that support its display.
ColumnMapping	Gets or sets how column data is written when it is saved as XML.
ColumnName	Gets or sets the name of the column.
DataType	Gets or sets the data type of the column data as one of the .NET Framework data types.
DefaultValue	Gets or sets the value that is automatically assigned to the column when a new row is created.
Expression	Gets or sets an expression that calculates the value of the column.
MaxLength	Gets or sets the maximum length for a column with a text data type in characters.
Namespace	Gets or sets the XML namespace for the XML representation of the data stored in the column.
Ordinal	Gets the position of the column within the column collection of the table.
Prefix	Gets or sets the XML prefix for the XML representation of the data stored in the column.
ReadOnly	Gets or sets a value that indicates whether the data in the column can be changed once the row containing the column is added to a table.
Table	Gets the table that the column has been assigned to.
Unique	Gets or sets a value indicating whether the value for each row in the column must be unique.

The commonly used public collections of the DataColumn class are listed in Table 24-2.

Table 24-2. DataColumn collections

Collection	Description
ExtendedProperties	The ExtendedProperties property accesses the PropertyCollection collection that contains custom information for the DataColumn as a collection of key and value pairs.

The DataColumn class is contained within the System.Data namespace. The DataColumn class inherits from MarshalByValueComponent. It's safe for multithreaded read operations; multithreaded write operations must be synchronized. DataColumn objects cannot be passed between different application domains.