无法将类型 'System.Byte' 的对象转换为类型 'System.String'

Question

在通过过滤将 Datatable 转换为 Dataview 时查询我的 SQL 数据库以将详细信息提取到 Dataset 中，因为是 Linq 的新手，我收到基本转换错误。

代码：

DataView cktDv = (from clounceform in dsclounceForms.Tables["Table2"].AsEnumerable()
                                         where clounceform.Field<string>("Form_FileType_ID").Equals("5")
                                         select clounceform).CopyToDataTable().AsDataView();

例外是

Unable to cast object of type 'System.Byte' to type 'System.String'.
System.Data.DataSetExtensions
at System.Data.DataRowExtensions.UnboxT`1.ReferenceField(Object value)
at System.Data.DataRowExtensions.Field[T](DataRow row, String columnName)
at ClounceFormsSuite.Design.CreateFormDesign.<>c.<CreateForm>b__12_0(DataRow bounceform) in myprojectfolderpath\CreateFormDesign.xaml.cs:line 115
at System.Linq.Enumerable.WhereEnumerableIterator`1.MoveNext()
at System.Data.DataTableExtensions.LoadTableFromEnumerable[T](IEnumerable`1 source, DataTable table, Nullable`1 options, FillErrorEventHandler errorHandler)
at System.Data.DataTableExtensions.CopyToDataTable[T](IEnumerable`1 source)
at ClounceFormsSuite.Design.CreateFormDesign.CreateForm(String[] cktFileContent, String filePath, String formID) in myprojectfolderpath\CreateFormDesign.xaml.cs:line 114
at ClounceFormsSuite.Design.CreateFormDesign.UserControl_Loaded(Object sender, RoutedEventArgs e) in myprojectfolderpath\CreateFormDesign.xaml.cs:line 70

我无法继续进行，我实际上将字符串转换为 int 并给出了不同的错误，这更误导了我当尝试转换为 int

DataView cktDataView = (from clounceform in dsclounceForms.Tables["Table2"].AsEnumerable()
                                         where clounceform.Field<int>("Form_FileType_ID") == 5
                                         select clounceform).CopyToDataTable().AsDataView();

错误：

 Specified cast is not valid.

Answer 1

数据是 byte，不是 string，也不是 int。因此，您需要使用 Field<byte>(...):

我怀疑这会起作用：

where clounceform.Field<byte>("Form_FileType_ID") == (byte)5

无法将类型 'System.Byte' 的对象转换为类型 'System.String'

Unable to cast object of type 'System.Byte' to type 'System.String'

c#

linq

wpf

linq-to-dataset