asp.net sql error running a select statement

[kajack]

i follow the tutorial from youtube writing a code of login & registration but got errors.\[code\]using System;using System.Collections.Generic;using System.Linq;using System.Web;using System.Web.UI;using System.Web.UI.WebControls;using System.Data.SqlClient;using System.Configuration;public partial class Registration : System.Web.UI.Page{ protected void Page_Load(object sender, EventArgs e) { if (IsPostBack) { SqlConnection con = new SqlConnection(ConfigurationManager.ConnectionStrings["earchConnectionString"].ConnectionString); con.Open(); string cmdStr = "Select count(*) from user where UserName='" + TextBoxUN.Text + "'"; SqlCommand userExist = new SqlCommand(cmdStr, con); int temp = Convert.ToInt32(userExist.ExecuteScalar().ToString()); con.Close(); if (temp == 1) { Response.Write("User Name Already Exist....<br /> Please Choose Another User Name."); } } } protected void Submit_Click(object sender, EventArgs e) { /*if (IsPostBack) { Response.Write("You have successfully registered"); }*/ SqlConnection con = new SqlConnection(ConfigurationManager.ConnectionStrings["earchConnectionString"].ConnectionString); con.Open(); string insCmd = "Insert into user (UserName, Password, EmailAddress, FullName, level) values (@UserName,@Password,@EmailAddress, @FullName, @level)"; SqlCommand insertUser = new SqlCommand(insCmd, con); insertUser.Parameters.AddWithValue("@UserName", TextBoxUN.Text); insertUser.Parameters.AddWithValue("@Password", TextBoxPass.Text); insertUser.Parameters.AddWithValue("@EmailAddress", TextBoxEA.Text); insertUser.Parameters.AddWithValue("@FullName", TextBoxFN.Text); insertUser.Parameters.AddWithValue("@level", level.SelectedItem.ToString()); try { insertUser.ExecuteNonQuery(); con.Close(); Response.Redirect("Login.aspx"); } catch (Exception er) { Response.Write("Something wrong"); } finally { //Any Special Action You Want To Add } }}\[/code\]but there is error messages:Incorrect syntax near the keyword 'user'.Description: An unhandled exception occurred during the execution of the current web request. Please review the stack trace for more information about the error and where it originated in the code. Exception Details: System.Data.SqlClient.SqlException: Incorrect syntax near the keyword 'user'.Source Error: Line 18: string cmdStr = "Select count(*) from user where UserName='" + TextBoxUN.Text + "'";Line 19: SqlCommand userExist = new SqlCommand(cmdStr, con);Line 20: int temp = Convert.ToInt32(userExist.ExecuteScalar().ToString());Line 21: con.Close();Line 22: if (temp == 1)Source File: c:\inetpub\web1\Registration.aspx.cs Line: 20 Stack Trace: [SqlException (0x80131904): Incorrect syntax near the keyword 'user'.] System.Data.SqlClient.SqlConnection.OnError(SqlException exception, Boolean breakConnection) +2042118 System.Data.SqlClient.SqlInternalConnection.OnError(SqlException exception, Boolean breakConnection) +5043644 System.Data.SqlClient.TdsParser.ThrowExceptionAndWarning() +234 System.Data.SqlClient.TdsParser.Run(RunBehavior runBehavior, SqlCommand cmdHandler, SqlDataReader dataStream, BulkCopySimpleResultSet bulkCopyHandler, TdsParserStateObject stateObj) +2294 System.Data.SqlClient.SqlDataReader.ConsumeMetaData() +33 System.Data.SqlClient.SqlDataReader.get_MetaData() +86 System.Data.SqlClient.SqlCommand.FinishExecuteReader(SqlDataReader ds, RunBehavior runBehavior, String resetOptionsString) +311 System.Data.SqlClient.SqlCommand.RunExecuteReaderTds(CommandBehavior cmdBehavior, RunBehavior runBehavior, Boolean returnStream, Boolean async) +987 System.Data.SqlClient.SqlCommand.RunExecuteReader(CommandBehavior cmdBehavior, RunBehavior runBehavior, Boolean returnStream, String method, DbAsyncResult result) +162 System.Data.SqlClient.SqlCommand.RunExecuteReader(CommandBehavior cmdBehavior, RunBehavior runBehavior, Boolean returnStream, String method) +32 System.Data.SqlClient.SqlCommand.ExecuteScalar() +139 Registration.Page_Load(Object sender, EventArgs e) in c:\inetpub\web1\Registration.aspx.cs:20 System.Web.Util.CalliHelper.EventArgFunctionCaller(IntPtr fp, Object o, Object t, EventArgs e) +14 System.Web.Util.CalliEventHandlerDelegateProxy.Callback(Object sender, EventArgs e) +35 System.Web.UI.Control.OnLoad(EventArgs e) +91 System.Web.UI.Control.LoadRecursive() +74 System.Web.UI.Page.ProcessRequestMain(Boolean includeStagesBeforeAsyncPoint, Boolean includeStagesAfterAsyncPoint) +2207What's the problem?