C# calling User Defined Scalar function in SQL Server that takes table type as its Parameter

Question

I have been beating my head against a rock on this. I have written a scalar function that takes a table type I created as a parameter and it returns a simple varchar here is the sql code if it helps

ALTER FUNCTION [dbo].[pe_Get_Manufacturer]
(
-- Add the parameters for the function here
@Row [dbo].[pe_StringList] READONLY
)

RETURNS VARCHAR(103)
AS
BEGIN

DECLARE @OUT VARCHAR(50)
DECLARE @tempTable TABLE
(
    Position INT,
    ManuName CHAR(100),
    ManuCat CHAR(3)
)

INSERT INTO @tempTable
    SELECT DISTINCT r.Position, c.ima_mfg, c.ima_cat
    FROM dbo.[Admin_ MFR Aliases] as c
        INNER JOIN @Row r
            ON c.orig_mfg = r.Candidate 
            OR c.ima_mfg = r.Candidate
            OR c.orgmfgstrp = r.Candidate
    ORDER BY r.Position

SELECT TOP 1 @OUT = LTRIM(RTRIM(ManuName))  + '^' + COALESCE(ManuCat,'')
FROM @tempTable 
ORDER BY Position DESC

-- Return the result of the function
RETURN @OUT
END

on my C# side I have a funcation that takes is a list of strings that is to be put into a Datatable to to be used as the parameter for the function. I believe I have written this is all correctly how ever my project throws when it goes to run ExecuteScalar on the SQLCommand

public string getManufacturer(IList<string> list)
    {

        int counter = 1;
        DataTable dataTable = new DataTable();
        dataTable.Columns.Add("Position", typeof (int));
        dataTable.Columns.Add("Candidate", typeof (string));

        foreach (var candidate in list)
        {
            DataRow dataRow = dataTable.NewRow();
            dataRow["Position"] = counter++;
            dataRow["Candidate"] = candidate;
            dataTable.Rows.Add(dataRow);
        }

        SqlParameter tableType = new SqlParameter("@Row" , SqlDbType.Structured)
        {
            TypeName = "dbo.pe_StringList",
            Value = dataTable
        };

        string query = " SELECT * FROM dbo.pe_Get_Manufacturer(@Row)";

        SqlCommand sqlCommand = new SqlCommand(query, conn);
        sqlCommand.Parameters.AddWithValue("@Row", tableType);

        return sqlCommand.ExecuteScalar().ToString();

    }

This is the information I get from the exception:

"An exception of type 'System.ArgumentException' occurred in System.Data.dll but was not handled in user code

Additional information: No mapping exists from object type System.Data.SqlClient.SqlParameter to a known managed provider native type."

EDIT---- this is the table type I created

CREATE TYPE pe_StringList
AS TABLE 
(
    Position INT,
    Candidate VARCHAR(50)
)

I changed the query from

string query = " SELECT * FROM dbo.pe_Get_Manufacturer(@Row)";

To

string query = " SELECT dbo.pe_Get_Manufacturer(@Row)";

Answer 1

Simply change:

sqlCommand.Parameters.AddWithValue("@Row", tableType);

to be:

sqlCommand.Parameters.Add(tableType);

since it is already a SqlParameter type. You would use AddWithValue to create the SqlParameter on-the-fly (though please see my note at the bottom about not using that deprecated method), but you have already created the SqlParameter and just need to add it to the collection.

And yes, removing the * FROM from the query was also necessary from a purely T-SQL syntax stand-point.

---

Side note: it is best to not use AddWithValue in any case, ever ;-):

• Difference between Parameters.Add and Parameters.AddWithValue
• Can we stop using AddWithValue() already?

Answer 2

Try changing

sqlCommand.Parameters.AddWithValue("@Row", tableType);

to

sqlCommand.Parameters.AddWithValue("@Row", dataTable);

You're setting the value of the Parameter you're adding with value to a SqlParameter which is not needed.

SqlParameterCollection.AddWithValue Method