C＃的DataTable小數精度

Question

我有這樣的代碼來新列添加到數據表：

 
DataColumn col = new DataColumn("column", typeof(decimal));  
col.Caption = "Column"; 
mytable.Columns.Add(col); 

如何指定此列小數精度所以價值總是會在我希望它是格式？

Answer 1

你不能。但是，您可以格式化值，當您使用String.Format函數從表中檢索：

String.Format("{0:0.##}", (Decimal) myTable.Rows[rowIndex].Columns[columnIndex]); 

Answer 2

我有同樣的問題我自己，我通過加載應用程序啓動時的整個架構，然後引用列固定它根據需要從架構獲取信息。

我只有一個Visual Basic例子，但希望它是很容易轉換成C＃

設置

' in whatever class you do your database communication: 
Private _database As SqlDatabase 
Private Shared _schema As DataTable 

Sub New() 
    ' or however you handle the connection string/database creation 
    Dim connectionString as String = GetConnectionString() 
    _database = New SqlDatabase(connectionString) 

    RetrieveSchema() 
End Sub 


Private Function RetrieveSchema() as DataTable 
    If _schema Is Nothing Then 
    Using connection As SqlConnection = _database.CreateConnection() 
     connection.Open() 
     _schema = connection.GetSchema("Columns") 
    End Using 
    End If 

    return _schema 
End Function 


Public Function GetColumnInformation(tableName As String, columnName As String) as DataRow 
    Dim firstMatchingRow as DataRow = (
    From row In _schema.Rows _ 
    Where (
     row("TABLE_NAME") = tableName AndAlso row("COLUMN_NAME") = columnName) 
    )).FirstOrDefault() 

    Return firstMatchingRow 
End Function 

使用

Dim columnInformation As DataRow = Dal.GetColumnInformation(tableName, columnName) 

' find the precision 
Dim precision = columnInformation("NUMERIC_PRECISION") 
Dim scale = columnInformation("NUMERIC_SCALE") 

' convert the decimal to the column's format 
' e.g.: 2.345 with a scale of 2 would result in 
'  2.35 
value = Decimal.Round(value, scale)