C# C/SQL解析错误

我正在尝试使用C和SQL构建一个注册用户脚本。然而，当我尝试向数据库添加用户详细信息时，我遇到了一个解析错误。此错误如下所示

There was an error parsing the query. [ Token line number = 1,Token line offset = 38,Token in error = = ]

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.SqlServerCe.SqlCeException: There was an error parsing the query. [ Token line number = 1,Token line offset = 38,Token in error = = ]

Source Error: 


Line 48:         {
Line 49:             var db = Database.Open("Database");
Line 50:             var users = db.QuerySingle("SELECT * FROM Users WHERE Username =  ", username);
Line 51:             if (users == null)
Line 52:             {

Source File: c:\Users\***\Documents\Visual Studio 2012\WebSites\CatSystem\Account\Login.cshtml    Line: 50 

Stack Trace: 


[SqlCeException (0x80004005): There was an error parsing the query. [ Token line number = 1,Token line offset = 38,Token in error = = ]]
   System.Data.SqlServerCe.SqlCeCommand.ProcessResults(Int32 hr) +136
   System.Data.SqlServerCe.SqlCeCommand.CompileQueryPlan() +798
   System.Data.SqlServerCe.SqlCeCommand.ExecuteCommand(CommandBehavior behavior, String method, ResultSetOptions options) +363
   System.Data.SqlServerCe.SqlCeCommand.ExecuteReader(CommandBehavior behavior) +59
   System.Data.SqlServerCe.SqlCeCommand.ExecuteDbDataReader(CommandBehavior behavior) +41
   System.Data.Common.DbCommand.ExecuteReader() +12
   WebMatrix.Data.<QueryInternal>d__0.MoveNext() +152
   System.Linq.Enumerable.FirstOrDefault(IEnumerable`1 source) +164
   WebMatrix.Data.Database.QuerySingle(String commandText, Object[] args) +103
   ASP._Page_Account_Login_cshtml.Execute() in c:\Users\***\Documents\Visual Studio 2012\WebSites\CatSystem\Account\Login.cshtml:50
   System.Web.WebPages.WebPageBase.ExecutePageHierarchy() +197
   System.Web.WebPages.WebPage.ExecutePageHierarchy(IEnumerable`1 executors) +69
   System.Web.WebPages.WebPage.ExecutePageHierarchy() +151
   System.Web.WebPages.StartPage.RunPage() +17
   System.Web.WebPages.StartPage.ExecutePageHierarchy() +62
   System.Web.WebPages.WebPageBase.ExecutePageHierarchy(WebPageContext pageContext,     TextWriter writer, WebPageRenderingBase startPage) +76
   System.Web.WebPages.WebPageHttpHandler.ProcessRequestInternal(HttpContext context) +249

Version Information: Microsoft .NET Framework Version:4.0.30319; ASP.NET     Version:4.0.30319.18010

我使用的脚本是

@{// Initialize page
var email = "";
var username = "";
var password = "";
var confirmPassword = "";
var firstname = "";
var lastname = "";
var housenumberorname = "";
var street = "";
var city = "";
var county = "";
var postcode = "";
var tel = "";
var mobile = "";
var dob = "";
var ErrorMessage = "";

// If this is a POST request, validate and process data
if (IsPost)
{
    email = Request.Form["email"];
    username = Request.Form["username"];
    password = Request.Form["password"];
    confirmPassword = Request.Form["confirmPassword"];
    firstname = Request.Form["firstname"];
    lastname = Request.Form["lastname"];
    housenumberorname = Request.Form["housenumberorname"];
    street = Request.Form["street"];
    city = Request.Form["city"];
    county = Request.Form["county"];
    postcode = Request.Form["postcode"];
    tel = Request.Form["tel"];
    mobile = Request.Form["mobile"];
    dob = Request.Form["dob"]; 

    if (username.IsEmpty() || password.IsEmpty()) {
        ErrorMessage = "You must specify both email and password.";
    } 

    if (password != confirmPassword) 
    {
        ErrorMessage = "Password and confirmation do not match.";
    }


    // If all information is valid, create a new account
    if (ErrorMessage=="")
    {
        var db = Database.Open("Database");
        var user = db.QuerySingle("SELECT * FROM Users WHERE Username = ", username);
        if (user == null)
        {
            db.Execute("INSERT INTO User (Username, Password, Firstname, Lastname, House, Street, City, County, Postscode, Tel, Mobile, Email, Dob) VALUES (@0, @1, @2, @3, @4, @5, @6, @7, @8, @9, @10, @11, @12)", username, password, firstname, lastname, housenumberorname, street, city, county, postcode, tel, mobile, email, dob);
            WebSecurity.CreateAccount(username, password, false);

            // Navigate back to the homepage and exit
            Response.Redirect("~/");
        } 
        else 
        {
            ErrorMessage = "Email address is already in use.";
        }
    }
}
}

@if (ErrorMessage!="")
{
<p>@ErrorMessage</p> 
<p>Please correct the errors and try again.</p>
}

我假设SQL命令有问题，但由于我不熟悉MS SQL，所以看不出问题所在。如果您对此有任何帮助，我们将不胜感激。

SQL无效。如果Username是VARCHAR或CHAR类型，则需要将值括在'，不过更好的选择是使用，因为使用字符串连接/格式化意味着您的应用程序可以打开

---

您应该更改代码以使用插入中的参数化：

var user = db.QuerySingle("SELECT * FROM Users WHERE Username = @0", username);

当前，您的查询不包含用户名中的用户名，它只是

SELECT * FROM Users WHERE Username =

这是无效的税收

发件人：

SELECT * FROM Users WHERE Username =

var db = Database.Open("TDL");
var selectQueryString = "SELECT * FROM Articles WHERE slug = @0";
show =  db.QuerySingle(selectQueryString, slug);