TFS Build 2.0 C#, howto add variables to the build/Pass Msbuild args

Question

I am trying to pass arguments to MSBuild 2.0. After research it appears that I need to do this using variables, but I cannot figure out how to incorporate this into my queue request below. I have tried parameters but that does not seem to work. Here is what I am trying to tell MSBuild @" /p:OctoPackPackageVersion=" + releaseNumber. This worked with the XAML build using IBuildRequest.ProcessParameters.

var buildClient = new BuildHttpClient(new Uri(collectionURL), new 
VssCredentials(true));
var res = await buildClient.QueueBuildAsync(new Build
            {
                Definition = new DefinitionReference
                {
                    Id = targetBuild.Id
                },
                Project = targetBuild.Project,
                SourceVersion = ChangeSetNumber,
                Parameters = buildArg

            });
            return res.Id.ToString();

Answer 1

vNext build system is different with legacy XAML build system, you cannot pass variable to build tasks in the build definition directly when queue the build. The code you used updated the build definition before queue the build which means that the build definition may keep changing if the variable changed.

The workaround for this would be add a variable in your build definition for example "var1" and then use this variable as the arguments for MSBuild Task: With this, you will be able to pass the value to "var1" variable when queue the build without updating the build definition.

Build build = new Build();
build.Parameters = "{\"var1\":\"/p:OctoPackPackageVersion=version2\"}";

// OR using Newtonsoft.Json.JsonConvert
var dict = new Dictionary<string, string>{{"var1", "/p:OctoPackPackageVersion=version2"}};
build.Parameters = JsonConvert.SerializeObject(dict)

Answer 2

I have found this solution and it works for me excellent. I set custom parameters for convenience in build definition without updating on server:

foreach (var variable in targetBuildDef.Variables.Where(p => p.Value.AllowOverride))
        {
            var customVar = variables.FirstOrDefault(p => p.Key == variable.Key);
            if (customVar == null)
                continue;
            variable.Value.Value = customVar.Value.TrimEnd('\\');
        }

And then set variables values in build parameters:

        using (TfsTeamProjectCollection ttpc = new TfsTeamProjectCollection(new Uri(tFSCollectionUri)))
        {
            using (BuildHttpClient buildServer = ttpc.GetClient<BuildHttpClient>())
            {
                var requestedBuild = new Build
                {
                    Definition = targetBuildDef,
                    Project = targetBuildDef.Project
                };
                var dic = targetBuildDef.Variables.Where(z => z.Value.AllowOverride).Select(x => new KeyValuePair<string, string>(x.Key, x.Value.Value));
                var paramString = $"{{{string.Join(",", dic.Select(p => $@"""{p.Key}"":""{p.Value}"""))}}}";
                var jsonParams = HttpUtility.JavaScriptStringEncode(paramString).Replace(@"\""", @"""");
                requestedBuild.Parameters = jsonParams;
                var queuedBuild = buildServer.QueueBuildAsync(requestedBuild).Result;