c#中是可以操作windows的磁盘配额的。具体方式如下：

1. 使用.net framework的WMI类库

示例代码：

using System;
using System.Management;
namespace DiskQuota
{
    class Class1
    {
        [STAThread]
        static void Main(string[] args)
        {
            try
            {
                ManagementClass c = new ManagementClass("Win32_DiskQuota");
                ManagementObject quota = c.CreateInstance();
                quota["Limit"] = 400000000;
                quota["WarningLimit"] = 200000000;
                // Get user account object
                ManagementObject account = new
                ManagementObject("Win32_Account.Domain=TODAY20040216,Name=ASPNET");
                account.Get();
                // get disk object
                ManagementObject disk = new
                ManagementObject("Win32_LogicalDisk.DeviceId='F:'");
                disk.Get();
                quota["QuotaVolume"] = disk;
                quota["User"] = account;
                quota.Put(); // commit

                ManagementClass c = new ManagementClass("Win32_DiskQuota");
                Console.WriteLine(c.SystemProperties);
                foreach (ManagementObject o in c.GetInstances())
                    Console.WriteLine("Next : {0}", o.Path);
            }
            catch (Exception e)
            {
                Console.WriteLine("error:" + e);
            }
        }
    }
}

2、 直接使用windows的dskquota.dll COM类

vs里面导入引用这个dll：tlbimp %windir%\dskquota.dll /out:c:\DiskQuotaTypeLibrary.dll /namespace:DiskQuotaTypeLibrary

示例代码：

using System;
using DiskQuotaTypeLibrary;
namespace Ex3cut3.Libraries
{
    public class QuotaClass
    {
        private DiskQuotaControlClass _diskQuotaControl;

        //This path has to be in this format or 
        //else is going to give an error of invalid path
        private const string FILESHAREVOLUME = @"\\server\c$\";
        //"
        private const int MBTOBYTES = 1048576;

        public DiskQuotaControlClass DiskQuotaControl
        {
            get
            {
                if (this._diskQuotaControl == null)
                {
                    this._diskQuotaControl = new DiskQuotaControlClass();
                    //Initializes the control to the specified path
                    this._diskQuotaControl.Initialize(FILESHAREVOLUME, true);
                }
                return this._diskQuotaControl;
            }
        }

        public QuotaClass()
        {
        }

        /// <summary>
        /// Adds a user to the quota entries of the volume
        /// </summary>
        /// <PARAM name="userName">The name of the user to Add</PARAM>
        /// <PARAM name="userDomain">The domain that the user uses to logon</PARAM>
        /// <PARAM name="quotaLimit">The quota limit of this user</PARAM>
        public void Add(string userName, string userDomain, int quotaLimit)
        {
            DIDiskQuotaUser dskuser = null;
            //In some cases if you use name resolution, 
            //the application will give an error.
            this.DiskQuotaControl.UserNameResolution =
              UserNameResolutionConstants.dqResolveNone;
            //Here we had the user to the Quotas Entrys of 
            //the volume, we use user@domain.net the logon name of the user.
            //You can use the domain\user or just the user, 
            //but this works faster
            dskuser = this.DiskQuotaControl.AddUser(
              user.SAMAccountName + "@" + user.Domain);
            //here we set the limit of the quota, this is 
            //prepared to receive MB so i convert it to BYTES
            dskuser.QuotaLimit = (int)quotaLimit * MBTOBYTES;
            //here is the set of the warning limit
            dskuser.QuotaThreshold = (int)(quotaLimit / 1.2) * MBTOBYTES;
            dskuser = null;
        }

        /// <summary>
        /// Removes the user form the Quota Entries List
        /// </summary>
        /// <PARAM name="userName"></PARAM>
        public void Remove(string userName)
        {
            //Here we just use the user, and invoke 
            //the method DeleteUser from the control
            this.DiskQuotaControl.DeleteUser(this.GetUser(userName));
        }

        /// <summary>
        /// A private function to return the user object
        /// </summary>
        /// <PARAM name="userName">The user name</PARAM>
        /// <returns>A DIDiskQuotaUser Object 
        /// of the specified user</returns>
        private DIDiskQuotaUser GetUser(string userName)
        {
            //Invokes the method to find a user in a quota entry list
            return this.DiskQuotaControl.FindUser(userName);
        }

        /// <summary>
        /// Gets the quota of the user
        /// </summary>
        /// <PARAM name="userName">The user name</PARAM>
        /// <returns>A formatted string of the quota 
        /// limit of the user</returns>
        private string GetQuota(string userName)
        {
            //here we return the text of the quota limit
            //0.0 bytes, 0.0 Kb, 0.0 Mb etc
            return this.GetUser(userName).QuotaLimitText;
        }

        /// <summary>
        /// Gets the quota currently used by the user
        /// </summary>
        /// <PARAM name="userName">The user name </PARAM>
        /// <returns>A formatted string of the quota 
        /// used by the user</returns>
        private string GetQuotaUsed(string userName)
        {
            return this.GetUser(userName).QuotaUsedText;
        }

        /// <summary>
        /// Change the quota of a specified user
        /// </summary>
        /// <PARAM name="userName">The user name</PARAM>
        /// <PARAM name="quotaLimit">The new quota limit of the user</PARAM>
        private void ChangeQuota(string userName, int quotaLimit)
        {
            DIDiskQuotaUser dskuser = this.GetUser(userName);
            dskuser.QuotaLimit = quotaLimit * Support.Constants.CONVERTBTOMB;
            dskuser.QuotaThreshold = (quotaLimit / 1.2)
              * Support.Constants.CONVERTBTOMB;
        }
    }
}

补充如何启用磁盘配额：

    /// <summary> 
    /// 启用磁盘配额 
    /// </summary> 
    /// <returns> </returns> 
    public bool WakeUpDiskQuota(string Disk,long DefaultQuotaLimit,long DefaultQuotaThreshold) 
    { 
        try 
        { 
            //DiskQuotaTypeLibrary.QuotaStateConstants.dqStateEnforce; 启用 
            //DiskQuotaTypeLibrary.QuotaStateConstants.dqStateDisable; 停用 
            DiskQuotaControlClass diskQuotaControl = new DiskQuotaControlClass(); 
            diskQuotaControl.Initialize(Disk, true); 
            diskQuotaControl.DefaultQuotaLimit =DefaultQuotaLimit; 
            diskQuotaControl.DefaultQuotaThreshold = DefaultQuotaThreshold; 
            diskQuotaControl.QuotaState = DiskQuotaTypeLibrary.QuotaStateConstants.dqStateEnforce; 
            return true; 
        } 
        catch { return false; } 
    }