C# 检查数据表中是否存在值？
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Check if value exists in dataTable?
提问by valterriann
I have DataTable with two columns Authorand Bookname.
我有两列Author和Bookname 的DataTable 。
I want to check if the given string value Authoralready exists in the DataTable. Is there some built in method to check it, like for Arrays array.contains?
我想检查给定的字符串值Author 是否已经存在于 DataTable 中。是否有一些内置的方法来检查它，比如 Arrays array.contains？
采纳答案by Tim Schmelter
You can use LINQ-to-DataSetwith Enumerable.Any:
你可以用LINQ-to-DataSet与Enumerable.Any：
String author = "John Grisham";
bool contains = tbl.AsEnumerable().Any(row => author == row.Field<String>("Author"));
Another approach is to use DataTable.Select:
另一种方法是使用DataTable.Select：
DataRow[] foundAuthors = tbl.Select("Author = '" + searchAuthor + "'");
if(foundAuthors.Length != 0)
{
// do something...
}
Q: what if we do not know the columns Headers and we want to find if any cell value
PEPSIexist in any rows'c columns? I can loop it all to find out but is there a better way? –
问：如果我们不知道列标题，而我们想查找
PEPSI任何行的 c 列中是否存在任何单元格值怎么办？我可以循环查找，但有更好的方法吗？——
Yes, you can use this query:
是的，您可以使用此查询：
DataColumn[] columns = tbl.Columns.Cast<DataColumn>().ToArray();
bool anyFieldContainsPepsi = tbl.AsEnumerable()
.Any(row => columns.Any(col => row[col].ToString() == "PEPSI"));
回答by mservidio
You can use Linq. Something like:
您可以使用 Linq。就像是：
bool exists = dt.AsEnumerable().Where(c => c.Field<string>("Author").Equals("your lookup value")).Count() > 0;
回答by Blast_dan
you could set the database as IEnumberable and use linq to check if the values exist. check out this link
您可以将数据库设置为 IEnumberable 并使用 linq 检查值是否存在。看看这个链接
LINQ Query on Datatable to check if record exists
the example given is
给出的例子是
var dataRowQuery= myDataTable.AsEnumerable().Where(row => ...
you could supplement where with any
你可以用任何来补充 where
回答by Antonio Bakula
DataRow rw = table.AsEnumerable().FirstOrDefault(tt => tt.Field<string>("Author") == "Name");
if (rw != null)
{
// row exists
}
add to your using clause :
添加到您的 using 子句：
using System.Linq;
and add :
并添加：
System.Data.DataSetExtensions
System.Data.DataSetExtensions
to references.
到参考。
回答by Kibbee
You should be able to use the DataTable.Select()method. You can us it like this.
您应该能够使用DataTable.Select()方法。你可以这样我们。
if(myDataTable.Select("Author = '" + AuthorName.Replace("'","''") + '").Length > 0)
...
The Select() funciton returns an array of DataRows for the results matching the where statement.
Select() 函数为与 where 语句匹配的结果返回一个 DataRow 数组。
