Gets a value indicating whether the Column is required which means that it cannot be deleted and that each Row must always contain data for this Column.

Namespace:  ESRI.ArcGISExplorer.Data

Assembly:  ESRI.ArcGISExplorer (in ESRI.ArcGISExplorer.dll) Version: 2.0.0.1500 (2.0.0.1500)

Syntax

C#
public bool Required { get; }
Visual Basic (Declaration)
Public ReadOnly Property Required As Boolean

Field Value

trueTruetruetrue (True in Visual Basic) if the Column has been defined as being required; otherwise, falseFalsefalsefalse (False in Visual Basic).

Examples

The code below provides a number of examples for working with ColumnCollection and Column properties. The second example prints out the Required property for the ObjectID column to confirm that it cannot be deleted and must always contain data.
CopyC#
//Open the Regions feature class stored in the Scotland file geodatabase
Geodatabase gdb = new Geodatabase(@"C:\Data\Scotland.gdb");
Table regionsTable = gdb.OpenTable("regions");

//Example 1 - column properties for the non-spatial, "Region" Column
Column regionColumn = regionsTable.Columns["Region"];

System.Diagnostics.Debug.Print(regionColumn.Name);               //Prints "Region"
System.Diagnostics.Debug.Print(regionColumn.AliasName);          //Prints "Region"
System.Diagnostics.Debug.Print(regionColumn.Type.ToString());    //Prints "String"
System.Diagnostics.Debug.Print(regionColumn.Length.ToString());  //Prints "50"

//Check that the parent data container is a geodatabase as the IsNullable and Required column
//properties only apply to this data format
if (regionsTable.Parent is Geodatabase)
{
  System.Diagnostics.Debug.Print(regionColumn.IsNullable.ToString()); //Prints "True"
  System.Diagnostics.Debug.Print(regionColumn.Required.ToString());   //Prints "False"
}

//Example 2 - column properties for the non-spatial, "ObjectID" column
//Check that the Regions table has a unique identifier column
if (regionsTable.Columns.HasObjectIDColumn)
{
  //Get the unique identifier column 
  Column oidColumn = regionsTable.Columns[regionsTable.Columns.ObjectIDColumnName];

  System.Diagnostics.Debug.Print(oidColumn.Name);                   //Prints "OBJECTID"
  System.Diagnostics.Debug.Print(oidColumn.Required.ToString());    //Prints "True"
  System.Diagnostics.Debug.Print(oidColumn.IsNullable.ToString());  //Prints "False"
}

//Example 3 - column properties for the spatial, "Shape" column
//Check that the Regions table can contain vector data
if (regionsTable.IsSpatial)
{
  //Get the column that can store geometry
  Column shapeColumn = regionsTable.Columns[regionsTable.Columns.SpatialColumnName];
  System.Diagnostics.Debug.Print(shapeColumn.Name); //Prints "Shape"
  System.Diagnostics.Debug.Print(shapeColumn.CoordinateSystem.Name); //Prints "British_National_Grid"
  System.Diagnostics.Debug.Print(shapeColumn.HasZ.ToString());       //Prints "False"

  //check that this table can store Polygon geometries
  if (shapeColumn.GeometryType == GeometryType.Polygon)
  {
    //Get the column which stores the perimeter length of each geometry
    Column lengthCol = regionsTable.Columns[regionsTable.Columns.LengthColumnName];
    System.Diagnostics.Debug.Print(lengthCol.Name); //Prints "Shape_Length"

    //Gets the column which stores the area of each geometry
    Column areaCol = regionsTable.Columns[regionsTable.Columns.AreaColumnName];
    System.Diagnostics.Debug.Print(areaCol.Name); //Prints "Shape_Area"
  }
}
CopyVB.NET
'Open regions feature class stored in the Scotland file geodatabase
Dim gdb As Geodatabase = New Geodatabase("C:\Data\Scotland.gdb")
Dim regionsTable As Table = gdb.OpenTable("regions")

'Example 1 - column properties for the non-spatial "Region" Column
Dim regionColumn As Column = regionsTable.Columns.Item("Region")

System.Diagnostics.Debug.Print(regionColumn.Name)               'Prints "Region"
System.Diagnostics.Debug.Print(regionColumn.AliasName)          'Prints "Region"
System.Diagnostics.Debug.Print(regionColumn.Type.ToString())    'Prints "String"
System.Diagnostics.Debug.Print(regionColumn.Length.ToString())  'Prints "50"


'Check that the parent data container is a geodatabase as the IsNullable and Required column
'properties only apply to this data format
If TypeOf regionsTable.Parent Is Geodatabase Then
  System.Diagnostics.Debug.Print(regionColumn.IsNullable.ToString()) 'Prints "True"
  System.Diagnostics.Debug.Print(regionColumn.Required.ToString())   'Prints "False"
End If

'Example 2 - column properties for the non-spatial, "ObjectID" column
'check that the Regions table has a unique identifier column
If (regionsTable.Columns.HasObjectIDColumn) Then
  'Get the unique identifier column
  Dim oidColumn As Column = regionsTable.Columns.Item(regionsTable.Columns.ObjectIDColumnName)

  System.Diagnostics.Debug.Print(oidColumn.Name)                   'Prints "OBJECTID"
  System.Diagnostics.Debug.Print(oidColumn.Required.ToString())    'Prints "True"
  System.Diagnostics.Debug.Print(oidColumn.IsNullable.ToString())  'Prints "False"
End If

'Example 3 - column properties for the spatial, "Shape" column
'check that the Regions table can contain vector data
If regionsTable.IsSpatial Then
  'Get the column that can store geometry
  Dim shapeColumn As Column = regionsTable.Columns.Item(regionsTable.Columns.SpatialColumnName)
  System.Diagnostics.Debug.Print(shapeColumn.Name)                  'Prints "Shape"
  System.Diagnostics.Debug.Print(shapeColumn.CoordinateSystem.Name) 'Prints "British_National_Grid"
  System.Diagnostics.Debug.Print(shapeColumn.HasZ.ToString())       'Prints "False"


  'check that this table can store Polygon geometries
  If shapeColumn.GeometryType = GeometryType.Polygon Then
    'Get the column which stores the perimeter length of each geometry
    Dim lengthCol As Column = regionsTable.Columns.Item(regionsTable.Columns.LengthColumnName)
    System.Diagnostics.Debug.Print(lengthCol.Name) 'Prints "Shape_Length"


    'Gets the column which stores the area of each geometry
    Dim areaCol As Column = regionsTable.Columns.Item(regionsTable.Columns.AreaColumnName)
    System.Diagnostics.Debug.Print(areaCol.Name) 'Prints "Shape_Area"
  End If
End If

See Also