Example of how to determine latest assembly version and latest database version of FluentMigrator.

LatestAssemblyVersion.cs

using FluentMigrator;
using FluentMigrator.Infrastructure;
using FluentMigrator.Runner;
using FluentMigrator.Runner.Announcers;
using FluentMigrator.Runner.Extensions;
using FluentMigrator.Runner.Initialization;
using FluentMigrator.Runner.Initialization.AssemblyLoader;
using System;
using System.IO;
using System.Reflection;
using System.Collections.Generic;
using Microsoft.Build.Utilities;
using Microsoft.Build.Framework;

/// <summary>
/// Gets the latest FluentMigrator version number in the supplied migrations file.
/// </summary>
public class LatestAssemblyVersion : Task
{
	public LatestAssemblyVersion()
	{
	}

	private string migrationAssembly;
	private long version;

	public string Target { get { return migrationAssembly; } set { migrationAssembly = value; } }

	public string MigrationAssembly { get { return migrationAssembly; } set { migrationAssembly = value; } }

	public string Namespace { get; set; }

	public string Tags { get; set; }

	[Output]
	public string Version { get { return this.version.ToString(); } }


	public override bool Execute()
	{

		if (string.IsNullOrEmpty(migrationAssembly))
		{
			Log.LogError("You must specify a migration assembly");
			return false;
		}

		IAnnouncer announcer = new ConsoleAnnouncer();

		Log.LogMessage(MessageImportance.Low, "Creating Context");

		IRunnerContext runnerContext = new RunnerContext(announcer)
		{
			Target = Target,
			Namespace = Namespace,
			Tags = Tags.ToTags()
		};

		try
		{
			MigratorInfo info = new MigratorInfo(runnerContext);
			this.version = info.GetLatestAssemblyVersion();
		}
		catch (ProcessorFactoryNotFoundException ex)
		{
			Log.LogError("While finding the latest assembly version the following error was encountered: {0}", ex.Message);
			return false;
		}
		catch (Exception ex)
		{
			Log.LogError("While finding the latest assembly version the following error was encountered: {0}, {1}", ex.Message, ex.StackTrace);
			return false;
		}
		
		return true;
	}
}

LatestDatabaseVersion.cs

using FluentMigrator.Runner;
using FluentMigrator.Runner.Announcers;
using FluentMigrator.Runner.Extensions;
using FluentMigrator.Runner.Initialization;
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using Microsoft.Build.Utilities;
using Microsoft.Build.Framework;

/// <summary>
/// Gets the latest FluentMigrator version number in database of the supplied connection string.
/// </summary>
public class LatestDatabaseVersion : Task
{
	public LatestDatabaseVersion()
	{
	}

	private string databaseType;
	private string migrationAssembly;
	private long version;

	[Required]
	public string Connection { get; set; }

	public string ConnectionStringConfigPath { get; set; }

	public string Target { get { return migrationAssembly; } set { migrationAssembly = value; } }

	public string MigrationAssembly { get { return migrationAssembly; } set { migrationAssembly = value; } }

	public string Namespace { get; set; }

	public string Tags { get; set; }

	public string Database { get { return databaseType; } set { databaseType = value; } }

	public string DatabaseType { get { return databaseType; } set { databaseType = value; } }

	[Output]
	public string Version { get { return this.version.ToString(); } }


	public override bool Execute()
	{
		if (string.IsNullOrEmpty(databaseType))
		{
			Log.LogError("You must specific a database type. i.e. mysql or sqlserver");
			return false;
		}

		if (string.IsNullOrEmpty(migrationAssembly))
		{
			Log.LogError("You must specify a migration assembly");
			return false;
		}

		IAnnouncer announcer = new ConsoleAnnouncer();

		Log.LogMessage(MessageImportance.Low, "Creating Context");

		IRunnerContext runnerContext = new RunnerContext(announcer)
		{
			Database = databaseType,
			Connection = Connection,
			ConnectionStringConfigPath = ConnectionStringConfigPath,
			Target = Target,
			Namespace = Namespace,
			Tags = Tags.ToTags()
		};

		try
		{
			MigratorInfo info = new MigratorInfo(runnerContext);
			this.version = info.GetLatestDatabaseVersion();
		}
		catch (ProcessorFactoryNotFoundException ex)
		{
			Log.LogError("While finding the latest database version the following error was encountered: {0}", ex.Message);
			return false;
		}
		catch (Exception ex)
		{
			Log.LogError("While finding the latest database version the following error was encountered: {0}, {1}", ex.Message, ex.StackTrace);
			return false;
		}
		
		return true;
	}
}

MigratorInfo.cs

using FluentMigrator;
using FluentMigrator.Infrastructure;
using FluentMigrator.Runner;
using FluentMigrator.Runner.Announcers;
using FluentMigrator.Runner.Extensions;
using FluentMigrator.Runner.Initialization;
using FluentMigrator.Runner.Initialization.AssemblyLoader;
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Reflection;

/// <summary>
/// Retrieves information whether a migration is required and which direction (up/down).
/// </summary>
public class MigratorInfo
{
	protected IRunnerContext RunnerContext { get; private set; }

	public MigratorInfo(IRunnerContext runnerContext)
	{
		if (runnerContext == null)
		{
			throw new ArgumentNullException("runnerContext");
		}
		this.RunnerContext = runnerContext;
	}

	public long GetLatestAssemblyVersion()
	{
		if (string.IsNullOrEmpty(RunnerContext.Target))
		{
			throw new ArgumentException("You must specify a migration assembly");
		}

		Assembly assembly = AssemblyLoaderFactory.GetAssemblyLoader(RunnerContext.Target).Load();
		MigrationConventions conventions = new MigrationConventions();
		MigrationLoader loader = new MigrationLoader(conventions, assembly, RunnerContext.Namespace, RunnerContext.Tags);
		long result = 0;
		foreach (var migration in loader.FindMigrations())
		{
			if (result < migration.Version)
				result = migration.Version;
		}
		return result;
	}

	public long GetLatestDatabaseVersion()
	{
		if (string.IsNullOrEmpty(RunnerContext.Connection))
		{
			throw new ArgumentException("You must specify a database connection");
		}
		if (string.IsNullOrEmpty(RunnerContext.Database))
		{
			throw new ArgumentException("You must specify a database type. i.e. mysql or sqlserver");
		}
		if (string.IsNullOrEmpty(RunnerContext.Target))
		{
			throw new ArgumentException("You must specify a migration assembly");
		}

		var executor = new MigratorTaskExecutor(this.RunnerContext);
		executor.Initialize();

		var runner = (MigrationRunner)executor.MigrationRunner;
		long result = runner.VersionLoader.VersionInfo.Latest();
		runner.Processor.CommitTransaction();

		// Remove circular referenced object
		runner.VersionLoader.Runner = null;

		return result;
	}
}

MigratorTaskExecutor.cs

using FluentMigrator;
using FluentMigrator.Infrastructure;
using FluentMigrator.Runner;
using FluentMigrator.Runner.Initialization;
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;

/// <summary>
/// Custom task executor that allows access to the migration runner and initialize methods.
/// </summary>
public class MigratorTaskExecutor : TaskExecutor
{
	public MigratorTaskExecutor(IRunnerContext runnerContext) : base(runnerContext)
	{

	}

	public void Initialize()
	{
		base.Initialize();
	}

	public IMigrationRunner MigrationRunner { get { return Runner; } }
}