Bagikan melalui

INullable.IsNull Properti

  • Referensi

Definisi

Ruang nama:
System.Data.SqlTypes
Rakitan:
System.Data.Common.dll
Rakitan:
System.Data.SqlClient.dll
Rakitan:
System.Data.dll
Rakitan:
netstandard.dll

Menunjukkan apakah struktur null. Properti ini bersifat hanya baca.

public:
 property bool IsNull { bool get(); };
public bool IsNull { get; }
member this.IsNull : bool
Public ReadOnly Property IsNull As Boolean

Nilai Properti

Boolean

true jika nilai objek ini null. Sebaliknya, false.

Contoh

Contoh kode berikut membuat DataTable dengan dua kolom yang didefinisikan sebagai SqlInt32 dan SqlString. Kode menambahkan satu baris nilai yang diketahui, satu baris nilai null dan kemudian beralih melalui DataTable, menetapkan nilai ke variabel dan menampilkan output di jendela konsol.

static private void WorkWithSqlNulls()
{
    DataTable table = new DataTable();

    // Specify the SqlType for each column.
    DataColumn idColumn =
        table.Columns.Add("ID", typeof(SqlInt32));
    DataColumn descColumn =
        table.Columns.Add("Description", typeof(SqlString));

    // Add some data.
    DataRow nRow = table.NewRow();
    nRow["ID"] = 123;
    nRow["Description"] = "Side Mirror";
    table.Rows.Add(nRow);

    // Add null values.
    nRow = table.NewRow();
    nRow["ID"] = SqlInt32.Null;
    nRow["Description"] = SqlString.Null;
    table.Rows.Add(nRow);

    // Initialize variables to use when
    // extracting the data.
    SqlBoolean isColumnNull = false;
    SqlInt32 idValue = SqlInt32.Zero;
    SqlString descriptionValue = SqlString.Null;

    // Iterate through the DataTable and display the values.
    foreach (DataRow row in table.Rows)
    {
        // Assign values to variables. Note that you
        // do not have to test for null values.
        idValue = (SqlInt32)row["ID"];
        descriptionValue = (SqlString)row["Description"];

        // Test for null value in ID column.
        isColumnNull = idValue.IsNull;

        // Display variable values in console window.
        Console.Write("isColumnNull={0}, ID={1}, Description={2}",
            isColumnNull, idValue, descriptionValue);
        Console.WriteLine();
    }

Private Sub WorkWithSqlNulls()
    Dim table As New DataTable()

    ' Specify the SqlType for each column.
    Dim idColumn As DataColumn = _
      table.Columns.Add("ID", GetType(SqlInt32))
    Dim descColumn As DataColumn = _
      table.Columns.Add("Description", GetType(SqlString))

    ' Add some data.
    Dim row As DataRow = table.NewRow()
    row("ID") = 123
    row("Description") = "Side Mirror"
    table.Rows.Add(row)

    ' Add null values.
    row = table.NewRow()
    row("ID") = SqlInt32.Null
    row("Description") = SqlString.Null
    table.Rows.Add(row)

    ' Initialize variables to use when
    ' extracting the data.
    Dim isColumnNull As SqlBoolean = False
    Dim idValue As SqlInt32 = SqlInt32.Zero
    Dim descriptionValue As SqlString = SqlString.Null

    ' Iterate through the DataTable and display the values.
    For Each row In table.Rows
        ' Assign values to variables. Note that you 
        ' do not have to test for null values.
        idValue = CType(row("ID"), SqlInt32)
        descriptionValue = CType(row("Description"), SqlString)

        ' Test for null value with ID column
        isColumnNull = idValue.IsNull

        ' Display variable values in console window.
        Console.Write("isColumnNull={0}, ID={1}, Description={2}", _
          isColumnNull, idValue, descriptionValue)
        Console.WriteLine()
    Next row
End Sub

Contoh ini menampilkan hasil berikut:

isColumnNull=False, ID=123, Description=Side Mirror  
isColumnNull=True, ID=Null, Description=Null

Keterangan

Nilai default untuk setiap instans System.Data.SqlTypes adalah null. Gunakan IsNull properti untuk menguji nilai null.

Berlaku untuk

Lihat juga