Как использовать SQL Server с Node.js, используя Edge.js

Save your text file, and from a command prompt enter:

> node server-sql-query.js

Open your web browser, and navigate to http://localhost:8080. If all goes well, you should see a list of five users.

Option 2: Execute .NET code to query SQL Server

Edge.js supports only very basic parameterized Select, Insert, Update, and Delete statements. It does not currently support stored procedures or blocks of SQL code. So, if you need to do anything more than a trivial CRUD operation, you will need to implement that in .NET.

Remember, stay async

The Node.js execution model is a single-threaded event loop. So, it is very important that your .NET code honor this by being fully async. Otherwise, a blocking call to .NET would create havoc for Node.js.

Create a class library

Our first step is to create a sample class library in Visual Studio that we can compile to a .DLL and use with Edge.js.

— Open Visual Studio.
— Create a new Class Library project named

EdgeSampleLibrary

.
— Delete the automatically-generated

Class1.cs

file.
— Create a new class named Sample1.
— Copy & paste the following code into your

Sample1.cs

file.

using System;
using System.Collections.Generic;
using System.Data;
using System.Data.SqlClient;
using System.Threading.Tasks;

namespace EdgeSampleLibrary
{
        public class Sample1
    {
        public async Task<object> Invoke(object input)
        {
            // Edge marshalls data to .NET using an IDictionary<string, object>
            var payload = (IDictionary<string, object>) input;
            var pageNumber = (int) payload["pageNumber"];
            var pageSize = (int) payload["pageSize"];
            return await QueryUsers(pageNumber, pageSize);
        }

        public async Task<List<SampleUser>> QueryUsers(int pageNumber, int pageSize)
        {
            // Use the same connection string env variable
            var connectionString = Environment.GetEnvironmentVariable("EDGE_SQL_CONNECTION_STRING");
            if (connectionString == null)
                throw new ArgumentException("You must set the EDGE_SQL_CONNECTION_STRING environment variable.");

            // Paging the result set using a common table expression (CTE).
            // You may rather do this in a stored procedure or use an
            // ORM that supports async.
            var sql = @"
DECLARE @RowStart int, @RowEnd int;
SET @RowStart = (@PageNumber - 1) * @PageSize + 1;
SET @RowEnd = @PageNumber * @PageSize;

WITH Paging AS
(
    SELECT  ROW_NUMBER() OVER (ORDER BY CreateDate DESC) AS RowNum,
            Id, FirstName, LastName, Email, CreateDate
    FROM    SampleUsers
)
SELECT  Id, FirstName, LastName, Email, CreateDate
FROM    Paging
WHERE   RowNum BETWEEN @RowStart AND @RowEnd
ORDER BY RowNum;
";
            var users = new List<SampleUser>();

            using (var cnx = new SqlConnection(connectionString))
            {
                using (var cmd = new SqlCommand(sql, cnx))
                {
                    await cnx.OpenAsync();

                    cmd.Parameters.Add(new SqlParameter("@PageNumber", SqlDbType.Int) { Value = pageNumber });
                    cmd.Parameters.Add(new SqlParameter("@PageSize", SqlDbType.Int) { Value = pageSize });

                    using (var reader = await cmd.ExecuteReaderAsync(CommandBehavior.CloseConnection))
                    {
                        while (await reader.ReadAsync())
                        {
                            var user = new SampleUser
                            {
                                Id = reader.GetInt32(0),
                                FirstName = reader.GetString(1),
                                LastName = reader.GetString(2),
                                Email = reader.GetString(3),
                                CreateDate = reader.GetDateTime(4)
                            };
                           users.Add(user);
                        }
                    }
                }
            }
            return users;
        }
    }

    public class SampleUser
    {
        public int Id { get; set; }
        public string FirstName { get; set; }
        public string LastName { get; set; }
        public string Email { get; set; }
        public DateTime CreateDate { get; set; }
    }
}

([project]/bin/Debug/EdgeSampleLibrary.dll)

server-dotnet-query.js

var http = require('http');
var edge = require('edge');
var port = process.env.PORT || 8080;

// Set up the assembly to call from Node.js
var querySample = edge.func({
    assemblyFile: 'EdgeSampleLibrary.dll',
    typeName: 'EdgeSampleLibrary.Sample1',
    methodName: 'Invoke'
});

function logError(err, res) {
    res.writeHead(200, { 'Content-Type': 'text/plain' });
    res.write("Got error: " + err);
    res.end("");
}

http.createServer(function (req, res) {
    res.writeHead(200, { 'Content-Type': 'text/html' });

    // This is the data we will pass to .NET
    var data = { pageNumber: 2, pageSize: 3 };

    // Invoke the .NET function
    querySample(data, function (error, result) {
        if (error) { logError(error, res); return; }
        if (result) {
            res.write("<ul>");
            result.forEach(function(user) {
                res.write("<li>" + user.FirstName + " " + user.LastName + ": " + user.Email + "</li>");
            });
            res.end("</ul>");
        }
        else {
            res.end("No results");
        }
    });
}).listen(port);

console.log("Node server listening on port " + port);

> node server-dotnet-query.js

pageNumber

pageSize