Breyta

Deila með

DataColumn.DefaultValue Property

  • Reference

Definition

Namespace:
System.Data
Assembly:
System.Data.Common.dll
Assembly:
System.Data.dll
Assembly:
netstandard.dll
Source:
DataColumn.cs
Source:
DataColumn.cs
Source:
DataColumn.cs

Gets or sets the default value for the column when you are creating new rows.

public:
 property System::Object ^ DefaultValue { System::Object ^ get(); void set(System::Object ^ value); };
[System.ComponentModel.TypeConverter(typeof(System.Data.DefaultValueTypeConverter))]
public object DefaultValue { get; set; }
public object DefaultValue { get; set; }
[System.ComponentModel.TypeConverter(typeof(System.Data.DefaultValueTypeConverter))]
[System.Data.DataSysDescription("DataColumnDefaultValueDescr")]
public object DefaultValue { get; set; }
[<System.ComponentModel.TypeConverter(typeof(System.Data.DefaultValueTypeConverter))>]
member this.DefaultValue : obj with get, set
member this.DefaultValue : obj with get, set
[<System.ComponentModel.TypeConverter(typeof(System.Data.DefaultValueTypeConverter))>]
[<System.Data.DataSysDescription("DataColumnDefaultValueDescr")>]
member this.DefaultValue : obj with get, set
Public Property DefaultValue As Object

Property Value

Object

A value appropriate to the column's DataType.

Attributes
TypeConverterAttribute DataSysDescriptionAttribute

Exceptions

InvalidCastException

When you are adding a row, the default value is not an instance of the column's data type.

Examples

The following example creates several DataColumn objects that have different data types, and sets appropriate default values to each column.

Private Sub CreateColumns()
    Dim column As DataColumn
    Dim table As New DataTable
 
    column = New DataColumn
    With column
       .DataType = System.Type.GetType("System.String")
       .DefaultValue = "Address"
       .Unique = False
    End With
    table.Columns.Add(column)
    
    column = New DataColumn
    With column
       .DataType = System.Type.GetType("System.Int32")
       .DefaultValue = 100
    End With
    table.Columns.Add(column)
 
    column = New DataColumn
    With column
       .DataType = System.Type.GetType("System.DateTime")
       .DefaultValue = "1/1/2001"
    End With
    table.Columns.Add(column)
 
    Dim row As DataRow
    ' Add one row. Since it has default values, 
    ' no need to set values yet.
    row = table.NewRow
   
    table.Rows.Add(row)
 End Sub

Remarks

A default value is the value that is automatically assigned to the column when a DataRow is created (for example, the date and time when the DataRow was created.

When AutoIncrement is set to true, there can be no default value.

You can create a new row using the ItemArray property of the DataRow class and passing the method an array of values. This is a potential problem for a column with a default value because its value is generated automatically. To use the ItemArray property with such a column, place null in the column's position in the array. For more information, see the ItemArray property.

Applies to

See also