LINQ - 指定的转换在dataview使用中无效 [英] LINQ - Specified cast is not valid with dataview use
问题描述
我正在尝试根据传递的列获取行的存在。该列以数据库的形式显示为MultiSelect。
I am trying to get the presence of rows based on the passed col. The column is coming from the database as MultiSelect.
bool bCFPresent = IsMultiSelectCFPresent(dvDataTag, "MultiSelect");
public static bool IsPresent(DataView dvDataTag, string colName)
{
return ((from DataRowView drv in dvDataTag
where drv.Row.Field<short>(colName) == 1
select drv).Count() > 0 ? true : false);
}
但是我收到这个错误: -
But I am getting this error:-
System.InvalidCastException是用户代码未处理的
Message =指定的转换无效。
Source =System.Data.DataSetExtensions
StackTrace:
在System.Data.DataRowExtensions.UnboxT`1.ValueField(Object
值)
在系统。 Data.DataRowExtensions.Field [T](DataRow
row,String columnName)
System.InvalidCastException was unhandled by user code
Message="Specified cast is not valid." Source="System.Data.DataSetExtensions" StackTrace: at System.Data.DataRowExtensions.UnboxT`1.ValueField(Object value) at System.Data.DataRowExtensions.Field[T](DataRow row, String columnName)
请帮助。
推荐答案
问题似乎是名为 colName
的列的类型不能总而言之,你的代码似乎并没有太大的意义。每列的行数相同。相反,请尝试直接检查列,例如:
The problem seems to be that the type of the column named colName
can't be casted to a short...
Overall, your code doesn't seem to make a whole lot of sense. The number of rows is the same for each column. Instead, try to check for the column directly, e.g like this:
public static bool IsPresent(DataView dvDataTag, string colName)
{
return dvDataTag.Table.Columns.Cast<DataColumn>().
Any(c => c.ColumnName == colName);
}
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