c# - 如何在 C# 中使用 Npgsql 4.1.5.0 中的游标 INOUT 参数调用 PostgreSQL 13 存储过程（无函数）

Question

我有这个带有 IN char 参数和 INOUT 游标参数的存储过程：

CREATE OR REPLACE PROCEDURE SP_ObtenerFacturaPorNombreCliente(IN p_nombreCliente CHAR, INOUT p_cursorFacturas REFCURSOR)
LANGUAGE PLPGSQL 
AS 
$$
BEGIN
    OPEN p_cursorFacturas FOR
    SELECT "CodigoFactura", "NombreCliente", "DireccionCliente", "TelefonoCliente", "Fecha", "SubTotal", "Iva", "ValorIva", "Total", "Geografico", "Geometrico" FROM "Factura"
    WHERE "NombreCliente" = p_nombreCliente
    ORDER BY "CodigoFactura";
END
$$

在 C# 中使用 Npgsql 4.1.5.0 调用的存储过程：

NpgsqlConnection npgsqlConnection = new NpgsqlConnection("Server=127.0.0.1;Port=5432;Database=mybase;User Id=user;Password=password;");
npgsqlConnection.Open();
npgsqlConnection.TypeMapper.UseNetTopologySuite();
string sentencialSQL = "CALL SP_ObtenerFacturaPorNombreCliente(:p_nombreCliente, :p_cursorFacturas);";
NpgsqlCommand npgsqlCommand = new NpgsqlCommand(sentencialSQL, npgsqlConnection);
// ===============================
NpgsqlParameter npgsqlParameter1 = new NpgsqlParameter();
npgsqlParameter1.ParameterName = ":p_nombreCliente";
npgsqlParameter1.Value = "Perico de los palotes";
npgsqlParameter1.NpgsqlDbType = NpgsqlTypes.NpgsqlDbType.Text;
npgsqlParameter1.Direction = ParameterDirection.Input;
npgsqlCommand.Parameters.Add(npgsqlParameter1);
// -------------------
NpgsqlParameter npgsqlParameter2 = new NpgsqlParameter();
npgsqlParameter2.ParameterName = ":p_cursorFacturas";
npgsqlParameter2.Value = string.Empty;
npgsqlParameter2.NpgsqlDbType = NpgsqlTypes.NpgsqlDbType.Refcursor;
npgsqlParameter2.Direction = ParameterDirection.InputOutput;
npgsqlCommand.Parameters.Add(npgsqlParameter2);
// ===============================
npgsqlCommand.CommandType = CommandType.Text; // CommandType.StoredProcedure is with Function
NpgsqlDataReader npgsqlDataReader = npgsqlCommand.ExecuteReader();

与：npgsqlParameter2.Value = string.Empty;我有这个错误：

42601：<<:>> 处或附近的语法错误

与：npgsqlParameter2.Value = null;我有这个错误：

参数：p_cursorFacturas 必须设置

更新：

在@madreflection 的建议下，我改变null了，DBNull.Value但调用改变npgsqlParameter2为“<unnamed portal 1>”

NpgsqlConnection npgsqlConnection = new NpgsqlConnection("Server=127.0.0.1;Port=5432;Database=mybase;User Id=user;Password=password;");
npgsqlConnection.Open();
npgsqlConnection.TypeMapper.UseNetTopologySuite();
string sentencialSQL = "CALL SP_ObtenerFacturaPorNombreCliente(:p_nombreCliente, :p_cursorFacturas);";
NpgsqlCommand npgsqlCommand = new NpgsqlCommand(sentencialSQL, npgsqlConnection);
// ===============================
NpgsqlParameter npgsqlParameter1 = new NpgsqlParameter();
npgsqlParameter1.ParameterName = ":p_nombreCliente";
npgsqlParameter1.Value = "Perico de los palotes";
npgsqlParameter1.NpgsqlDbType = NpgsqlTypes.NpgsqlDbType.Text;
npgsqlParameter1.Direction = ParameterDirection.Input;
npgsqlCommand.Parameters.Add(npgsqlParameter1);
// -------------------
NpgsqlParameter npgsqlParameter2 = new NpgsqlParameter();
npgsqlParameter2.ParameterName = ":p_cursorFacturas";
npgsqlParameter2.Value = DBNull.Value;
npgsqlParameter2.NpgsqlDbType = NpgsqlTypes.NpgsqlDbType.Refcursor;
npgsqlParameter2.Direction = ParameterDirection.InputOutput;
npgsqlCommand.Parameters.Add(npgsqlParameter2);
// ===============================
npgsqlCommand.CommandType = CommandType.Text; // CommandType.StoredProcedure is with Function
NpgsqlDataReader npgsqlDataReader = npgsqlCommand.ExecuteReader();

Answer 1

好的，我想通了。这篇文章对我帮助很大。这是其他人的答案。

//transaction is needed to keep unnamed portal 1
var transaction = npgsqlConnection.BeginTransaction();

//create the command and add all the parameters, command type, etc 

...

npgsqlCommand.CommandType = CommandType.Text; 

npgsqlCommand.CommandText = "call your_procedure(:parameters)";

//execute the original procedure with ExecuteNonQuery
npgsqlCommand.ExecuteNonQuery();

//change the command text and execute the reader
npgsqlCommand.CommandText = "fetch all in \"<unnamed portal 1>\"";

var npgsqlDataReader = npgsqlCommand.ExecuteReader();

while (reader.Read())
{  
    // do whatever is needed to extract the data
}

//clean up
transaction.Commit();
npgsqlConnection.Close();