Convert.IsDBNull(Object) 메서드

정의

지정된 개체의 형식이 DBNull인지를 나타내는 값을 반환합니다.Returns an indication whether the specified object is of type DBNull.

public:
 static bool IsDBNull(System::Object ^ value);
public static bool IsDBNull (object value);
static member IsDBNull : obj -> bool
Public Shared Function IsDBNull (value As Object) As Boolean

매개 변수

value
Object

개체입니다.An object.

반환

true의 형식이 value이면 DBNull이고, 그렇지 않으면 false입니다.true if value is of type DBNull; otherwise, false.

예제

다음 예에서는 SqlDataReader 개체를 사용 하 여 데이터베이스에서 설문 조사 데이터를 검색 합니다.The following example uses a SqlDataReader object to retrieve survey data from a database. 각 행의 필드 값을 배열에 할당 한 다음 각 배열 요소를 IsDBNull 메서드에 전달 합니다.It assigns each row's field values to an array, and then passes each array element to the IsDBNull method. 메서드가 true을 반환 하는 경우이 예제에서는 문자열 "NA"를 배열 요소에 할당 합니다.If the method returns true, the example assigns the string "NA" to the array element. 그런 다음 System.Windows.Forms.DataGridView 컨트롤의 Rows 컬렉션에 배열을 추가 합니다.The array is then added to the Rows collection of a System.Windows.Forms.DataGridView control.

private void Form1_Load(object sender, EventArgs e)
{
   // Define ADO.NET objects.
   SqlConnection conn = new SqlConnection(connectionString);
   SqlCommand cmd = new SqlCommand();
   SqlDataReader dr;

   // Open connection, and retrieve dataset.
   conn.Open();

   // Define Command object.
   cmd.CommandText = "Select * From Responses";
   cmd.CommandType = CommandType.Text;
   cmd.Connection = conn;

   // Retrieve data reader.
   dr = cmd.ExecuteReader();

   int fieldCount = dr.FieldCount;
   object[] fieldValues = new object[fieldCount];
   string[] headers = new string[fieldCount];
    
   // Get names of fields.
   for (int ctr = 0; ctr < fieldCount; ctr++)
      headers[ctr] = dr.GetName(ctr);

   // Set up data grid.
   this.grid.ColumnCount = fieldCount;

   this.grid.ColumnHeadersDefaultCellStyle.BackColor = Color.Navy;
   this.grid.ColumnHeadersDefaultCellStyle.ForeColor = Color.White;
   this.grid.ColumnHeadersDefaultCellStyle.Font = new Font(this.grid.Font, FontStyle.Bold);

   this.grid.AutoSizeRowsMode = DataGridViewAutoSizeRowsMode.DisplayedCellsExceptHeaders;
   this.grid.ColumnHeadersBorderStyle = DataGridViewHeaderBorderStyle.Single;
   this.grid.CellBorderStyle = DataGridViewCellBorderStyle.Single;
   this.grid.GridColor = Color.Black;
   this.grid.RowHeadersVisible = true;

   for (int columnNumber = 0; columnNumber < headers.Length;  columnNumber++)
      this.grid.Columns[columnNumber].Name = headers[columnNumber];

   // Get data, replace missing values with "NA", and display it.
   while (dr.Read())
   {
      dr.GetValues(fieldValues);

      for (int fieldCounter = 0; fieldCounter < fieldCount; fieldCounter++)
      {
         if (Convert.IsDBNull(fieldValues[fieldCounter]))
            fieldValues[fieldCounter] = "NA";
      }
      grid.Rows.Add(fieldValues);
   }
   dr.Close();
}
Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
   ' Define ADO.NET objects.
   Dim conn As New SqlConnection(connectionString)
   Dim cmd As New SqlCommand
   Dim dr As SqlDataReader

   ' Open connection, and retrieve dataset.
   conn.Open()

   ' Define Command object.
   cmd.CommandText = "Select * From Responses"
   cmd.CommandType = CommandType.Text
   cmd.Connection = conn

   ' Retrieve data reader.
   dr = cmd.ExecuteReader()

   Dim fieldCount As Integer = dr.FieldCount
   Dim fieldValues(fieldCount - 1) As Object
   Dim headers(fieldCount - 1) As String

   ' Get names of fields.
   For ctr As Integer = 0 To fieldCount - 1
      headers(ctr) = dr.GetName(ctr)
   Next

   ' Set up data grid.
   grid.ColumnCount = fieldCount

   With grid.ColumnHeadersDefaultCellStyle
      .BackColor = Color.Navy
      .ForeColor = Color.White
      .Font = New Font(grid.Font, FontStyle.Bold)
   End With

   With grid
      .AutoSizeRowsMode = _
          DataGridViewAutoSizeRowsMode.DisplayedCellsExceptHeaders
      .ColumnHeadersBorderStyle = DataGridViewHeaderBorderStyle.Single
      .CellBorderStyle = DataGridViewCellBorderStyle.Single
      .GridColor = Color.Black
      .RowHeadersVisible = True

      For columnNumber As Integer = 0 To headers.Length - 1
         .Columns(columnNumber).Name = headers(columnNumber)
      Next
   End With

   ' Get data, replace missing values with "NA", and display it.
   Do While dr.Read()
      dr.GetValues(fieldValues)

      For fieldCounter As Integer = 0 To fieldCount - 1
         If Convert.IsDBNull(fieldValues(fieldCounter)) Then
            fieldValues(fieldCounter) = "NA"
         End If
      Next
      grid.Rows.Add(fieldValues)
   Loop
   dr.Close()
End Sub

설명

IsDBNull 메서드는 value 매개 변수가 DBNull.Value와 같은지 여부를 테스트 합니다.The IsDBNull method tests whether the value parameter is equal to DBNull.Value. 다음 코드는 동일 합니다.It is equivalent to the following code:

return DBNull.Value.Equals(value);
Return DBNull.Value.Equals(value)

참고

DBNull.Value은 누락 된 값을 나타내는 데 사용 됩니다.DBNull.Value is used to indicate a value that is missing. null 하거나 String.Empty하는 것과는 동일 하지 않습니다.It is not equivalent to null or to String.Empty. 따라서 Visual Basic Convert.IsDBNull(Nothing) C# 또는의 Convert.IsDBNull(null) 같은 코드는false를 반환 합니다.Therefore, code such as Convert.IsDBNull(null) in C# or Convert.IsDBNull(Nothing) in Visual Basic returnsfalse.

적용 대상

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