C＃数据表精度十进制

问题描述

| 我有以下代码将新列添加到数据表中： DataColumn col = new DataColumn（\“ column \”，typeof（decimal））; col.Caption = \“列\”; mytable.Columns.Add（col）; 如何为该列指定小数精度，以便该值始终采用我希望的格式？     

解决方法

        你不能。但是，使用

String.Format

函数从表中检索值时，可以设置其格式：

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

    ,        我自己也遇到了同样的问题，并通过在应用启动时加载整个架构来解决此问题，然后在需要时从该架构中引用列信息。 我只有一个Visual Basic示例，但希望它很容易转换为C＃ 设定

\' 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

用法

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)