Calling SQL Defined function in C#

Question

I have written this scalar function in TSQL:

create function TCupom (@cupom int)
returns float
as
begin
    declare @Tcu float;

    select @Tcu = sum (total) from alteraca2 where pedido = @cupom 

    if (@tcu is  null)
        set @tcu = 0;

    return @tcu;
end

I want to call this function in my C# code. Here's what I have so far:

public void TotalCupom(int cupom)
{ 
    float SAIDA;           
    SqlDataAdapter da2 = new SqlDataAdapter();

    if (conex1.State == ConnectionState.Closed)
    { 
        conex1.Open();
    }

    SqlCommand Totalf = new SqlCommand("Tcupom", conex1);
    SqlParameter code1 = new SqlParameter("@code", SqlDbType.Int);
    code1.Value = cupom ;
    Totalf.CommandType = CommandType.StoredProcedure ;
    SAIDA = Totalf.ExecuteScalar();

    return SAIDA;
}

Answer 1

You can't just call the function name, you will need to write an inline SQL statement which makes use of the UDF:

SqlCommand Totalf = new SqlCommand("SELECT dbo.Tcupom(@code)", conex1); 

And remove the CommandType, this isn't a Stored Procedure, its a User Defined Function.

In all:

public void TotalCupom(int cupom) {      float SAIDA;                SqlDataAdapter da2 = new SqlDataAdapter();     if (conex1.State == ConnectionState.Closed)     {         conex1.Open();     }     SqlCommand Totalf = new SqlCommand("SELECT dbo.Tcupom(@code)", conex1);     SqlParameter code1 = new SqlParameter("@code", SqlDbType.Int);     code1.Value = cupom;     SAIDA = Totalf.ExecuteScalar();      return SAIDA; } 

Answer 2

...

try
{
    if (connectionState != ConnectionState.Open)
        conn.Open();
    using (var cmd = conn.CreateCommand())
    {
        cmd.CommandText = "udfName";
        cmd.CommandType = CommandType.StoredProcedure;

        foreach (var cmdParam in sqlParams)
        {
            cmd.Parameters.Add(cmdParam);
        }


        var retValParam = new SqlParameter("RetVal", SqlDbType.Int)
        {
            //Set this property as return value
            Direction = ParameterDirection.ReturnValue 
        };

        cmd.Parameters.Add(retValParam);
        cmd.ExecuteScalar();

        retVal = retValParam.Value;
    }
}
finally
{
    if (connectionState == ConnectionState.Open)
        conn.Close();
}

...

Answer 3

I wanted to call a SQL Function in the same way that I call Stored Procedures which is by using DeriveParameters and then setting the parameter values. It turns out that this works with Scalar Functions out of the box and you can use ExecuteNonQuery and read the RETURN_VALUE. Please see sample code below:

    public int GetLookupCodeFromShortCode(short tableType, string shortCode)
    {
        using (var conn = new SqlConnection(ConfigurationManager.ConnectionStrings["Default"].ConnectionString))
        {
            conn.Open();

            using (var cmd = new SqlCommand("dbo.fnGetLookupCodeFromShortCode", conn))
            {
                cmd.CommandType = CommandType.StoredProcedure;
                cmd.CommandTimeout = 30;
                SqlCommandBuilder.DeriveParameters(cmd);

                cmd.Parameters["@sintTableType"].Value = tableType;
                cmd.Parameters["@vchrShortCode"].Value = shortCode;
                cmd.Parameters["@chrLanguage"].Value = "en";
                cmd.Parameters["@chrCountry"].Value = "en";

                cmd.ExecuteNonQuery();

                return (int)cmd.Parameters["@RETURN_VALUE"].Value;
            }
        }

    }

The Scalar Function code looks like this:

CREATE FUNCTION [dbo].[fnGetLookupCodeFromShortCode]( @sintTableType SMALLINT, @vchrShortCode VARCHAR(5), @chrLanguage CHAR(2), @chrCountry CHAR(2))

RETURNS INT

AS

BEGIN

    DECLARE @intLookupCode  INT

    SELECT @intLookupCode = LV.intLookupCode 
    FROM    
    tblLookupValueDesc LVD
        INNER JOIN tblLookupValue LV ON LV.sintLookupTableType = LVD.sintLookupTableType AND LV.intTableKey = LVD.intTableKey
    WHERE   
    LVD.sintLookupTableType = @sintTableType
    AND LVD.vchrShortCode = @vchrShortCode
    AND LVD.chrCountry = @chrCountry
    AND LVD.chrLanguage = @chrLanguage

    RETURN @intLookupCode 

END

GO