将DataTable转换为IEnumerable <T>
我正试图将DataTable转换为IEnumerable。 其中T是我创建的自定义类型。 我知道我可以通过创建一个List来做到这一点，但我认为有一种使用IEnumerable的方法。 这是我现在拥有的。
private IEnumerable<TankReading> ConvertToTankReadings(DataTable dataTable)
{
var tankReadings = new List<TankReading>();
foreach (DataRow row in dataTable.Rows)
{
var tankReading = new TankReading
{
TankReadingsID = Convert.ToInt32(row["TRReadingsID"]),
TankID = Convert.ToInt32(row["TankID"]),
ReadingDateTime = Convert.ToDateTime(row["ReadingDateTime"]),
ReadingFeet = Convert.ToInt32(row["ReadingFeet"]),
ReadingInches = Convert.ToInt32(row["ReadingInches"]),
MaterialNumber = row["MaterialNumber"].ToString(),
EnteredBy = row["EnteredBy"].ToString(),
ReadingPounds = Convert.ToDecimal(row["ReadingPounds"]),
MaterialID = Convert.ToInt32(row["MaterialID"]),
Submitted = Convert.ToBoolean(row["Submitted"]),
};
tankReadings.Add(tankReading);
}
return tankReadings.AsEnumerable();
}
关键部分是我创建一个列表，然后使用AsEnumerable（）返回它。
该实施没有任何问题。 你可以给yield关键字一个镜头，看看你喜欢它：
private IEnumerable<TankReading> ConvertToTankReadings(DataTable dataTable)
{
foreach (DataRow row in dataTable.Rows)
{
yield return new TankReading
{
TankReadingsID = Convert.ToInt32(row["TRReadingsID"]),
TankID = Convert.ToInt32(row["TankID"]),
ReadingDateTime = Convert.ToDateTime(row["ReadingDateTime"]),
ReadingFeet = Convert.ToInt32(row["ReadingFeet"]),
ReadingInches = Convert.ToInt32(row["ReadingInches"]),
MaterialNumber = row["MaterialNumber"].ToString(),
EnteredBy = row["EnteredBy"].ToString(),
ReadingPounds = Convert.ToDecimal(row["ReadingPounds"]),
MaterialID = Convert.ToInt32(row["MaterialID"]),
Submitted = Convert.ToBoolean(row["Submitted"]),
};
}
}
此外， AsEnumerable不是必需的，因为List<T>已经是一个IEnumerable<T>
还有一个叫做“AsEnumerable（）”的DataSetExtension方法（在System.Data中），它接受一个DataTable并返回一个Enumerable。 有关更多详细信息，请参阅MSDN文档，但它基本上如下所示：
dataTable.AsEnumerable()
缺点是它枚举DataRow，而不是你的自定义类。 “Select（）”LINQ调用可以转换行数据，但是：
private IEnumerable<TankReading> ConvertToTankReadings(DataTable dataTable)
{
return dataTable.AsEnumerable().Select(row => new TankReading
{
TankReadingsID = Convert.ToInt32(row["TRReadingsID"]),
TankID = Convert.ToInt32(row["TankID"]),
ReadingDateTime = Convert.ToDateTime(row["ReadingDateTime"]),
ReadingFeet = Convert.ToInt32(row["ReadingFeet"]),
ReadingInches = Convert.ToInt32(row["ReadingInches"]),
MaterialNumber = row["MaterialNumber"].ToString(),
EnteredBy = row["EnteredBy"].ToString(),
ReadingPounds = Convert.ToDecimal(row["ReadingPounds"]),
MaterialID = Convert.ToInt32(row["MaterialID"]),
Submitted = Convert.ToBoolean(row["Submitted"]),
});
}
使用System.Data.DataSetExtensions简单方法：
table.AsEnumerable().Select(row => new TankReading{
TankReadingsID = Convert.ToInt32(row["TRReadingsID"]),
TankID = Convert.ToInt32(row["TankID"]),
ReadingDateTime = Convert.ToDateTime(row["ReadingDateTime"]),
ReadingFeet = Convert.ToInt32(row["ReadingFeet"]),
ReadingInches = Convert.ToInt32(row["ReadingInches"]),
MaterialNumber = row["MaterialNumber"].ToString(),
EnteredBy = row["EnteredBy"].ToString(),
ReadingPounds = Convert.ToDecimal(row["ReadingPounds"]),
MaterialID = Convert.ToInt32(row["MaterialID"]),
Submitted = Convert.ToBoolean(row["Submitted"]),
});
要么：
TankReading TankReadingFromDataRow(DataRow row){
return new TankReading{
TankReadingsID = Convert.ToInt32(row["TRReadingsID"]),
TankID = Convert.ToInt32(row["TankID"]),
ReadingDateTime = Convert.ToDateTime(row["ReadingDateTime"]),
ReadingFeet = Convert.ToInt32(row["ReadingFeet"]),
ReadingInches = Convert.ToInt32(row["ReadingInches"]),
MaterialNumber = row["MaterialNumber"].ToString(),
EnteredBy = row["EnteredBy"].ToString(),
ReadingPounds = Convert.ToDecimal(row["ReadingPounds"]),
MaterialID = Convert.ToInt32(row["MaterialID"]),
Submitted = Convert.ToBoolean(row["Submitted"]),
};
}
// Now you can do this
table.AsEnumerable().Select(row => return TankReadingFromDataRow(row));
或者，更好的是，创建一个TankReading(DataRow r)构造函数，然后这变成：
table.AsEnumerable().Select(row => return new TankReading(row));