Note: I was unable to find this exact question in a search. I found a somewhat similar question here on Stack Overflow, which led me to the solution. I'm posting the question and the solution so that the next person with the problem can more easily find the solution. I would have made the question CommunityWiki if that were still possible - I'm not looking for rep from this.
I am trying to use ADO.NET to call a SQL Server 2005 stored procedure which accepts a parameter of the Xml
type:
CREATE PROCEDURE dbo.SomeProcedure(
@ListOfIds Xml)
AS
BEGIN
DECLARE
@Ids TABLE(ID Int);
INSERT INTO @Ids
SELECT ParamValues.ID.value('.', 'Int')
FROM @ListOfIds.nodes('/Persons/id') AS ParamValues(ID);
SELECT p.Id,
p.FirstName,
p.LastName
FROM Persons AS p
INNER JOIN @Ids AS i ON p.Id = i.ID;
END;
I pass the XML as a LINQ to XML XElement object
var idList = new XElement(
"Persons",
from i in selectedPeople
select new XElement("id", i));
later
SqlCommand cmd = new SqlCommand
{
Connection = conn,
CommandText = "dbo.SomeProcedure",
CommandType = CommandType.StoredProcedure
};
cmd.Parameters.Add(
new SqlParameter
{
ParameterName = "@ListOfIds",
SqlDbType = SqlDbType.Xml,
Value = idList)
});
using (var reader = cmd.ExecuteReader())
{
// process each row
}
This fails on the ExecuteReader
line with the exception:
System.InvalidCastException: Failed to convert parameter value from a XElement to a String. ---> System.InvalidCastException: Object must implement IConvertible
What's the correct way to pass an XElement
to a stored procedure?
The SqlClient code doesn't permit an XElement to be passed directly.
One thing you can do is to use the System.Data.SqlTypes.SqlXml
class to pass the XML:
cmd.Parameters.Add(
new SqlParameter
{
ParameterName = "@ListOfIds",
SqlDbType = SqlDbType.Xml,
Value = new SqlXml(idList.CreateReader())
});
Depending on your code, you may need to place the XmlReader
returned from the CreateReader
code into a using
block.
Here is two extension methods I built based on John Saunders' answer.
public static class ExtensionMethods
{
public static void AddXml(this SqlParameterCollection theParameters, string name, XElement value)
{
theParameters.Add(new SqlParameter()
{
ParameterName = name,
SqlDbType = SqlDbType.Xml,
Value = new SqlXml(value.CreateReader())
});
}
public static void AddXml(this SqlParameterCollection theParameters, string name, string value)
{
theParameters.Add(new SqlParameter()
{
ParameterName = name,
SqlDbType = SqlDbType.Xml,
Value = new SqlXml(XElement.Parse(value).CreateReader())
});
}
}
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