Error in query LINQ (Lambda Expression)

I have a query, which was working perfectly in my controller .

I made a change (I do not know which) and stopped working. I do not know what I did wrong, to stop working.

Error:

  

The string contains more than one matching element

Controlller :

public ActionResult Dependente(string name) {
    //Instancia obj da DLL
    Criptografia cr = new Criptografia();

    //Recebe oa string Criptografada
    string nome = Request.QueryString["param"];

    //Descriptografa a string
    string nomeDescrypt = cr.Decrypt(nome);

    //Separa a string por meio do "|"
    string[] stringSeparators = new string[] {
        "|"
    };
    var result = nomeDescrypt.Split(stringSeparators, StringSplitOptions.None);

    //Concerte para o tipo de dado correto
    var matricula = Convert.ToInt32(result[0]);
    var contrato = Convert.ToInt32(result[1]);

    //Salvar a session no Helper
    System.Web.HttpContext.Current.Session["Contrato"] = contrato; // valor do contrato = 11
    System.Web.HttpContext.Current.Session["Matricula"] = matricula; // valor da matricula = 9951

    var userMatricula = SessionHelper.Matricula; //valor da matricula = 9951

    var usuarios = usuarioRepository.Lista.Where(r = > r.CdMatricula == matricula && r.SqContrato == contrato).SingleOrDefault(); // valor da matricula: 9951, contrato: 11

    return View(usuarios);

}

By doing this same query in the database, I only get 1 result.

Error generated:

[InvalidOperationException: A sequência contém mais de um elemento de correspondência]
System.Linq.Enumerable.SingleOrDefault(IEnumerable'1 source, Func'2 predicate) +2533722
System.Data.Entity.Migrations.Infrastructure.<>c__DisplayClass250.    <FindAlteredColumns>b__247(<>f__AnonymousType2b'2 <>h__TransparentIdentifier242) +230
System.Linq.WhereSelectEnumerableIterator'2.MoveNext() +145
System.Linq.WhereSelectEnumerableIterator'2.MoveNext() +171
System.Collections.Generic.List'1..ctor(IEnumerable'1 collection) +381
System.Linq.Enumerable.ToList(IEnumerable'1 source) +58
System.Data.Entity.Migrations.Infrastructure.EdmModelDiffer.Diff(ModelMetadata source,     ModelMetadata target, Lazy'1 modificationCommandTreeGenerator, MigrationSqlGenerator     migrationSqlGenerator, String sourceModelVersion, String targetModelVersion) +640
System.Data.Entity.Migrations.Infrastructure.EdmModelDiffer.Diff(XDocument   sourceModel, XDocument targetModel, Lazy'1 modificationCommandTreeGenerator, MigrationSqlGenerator migrationSqlGenerator, String sourceModelVersion, String targetModelVersion) +870
System.Data.Entity.Internal.InternalContext.ModelMatches(VersionedModel model) +151 System.Data.Entity.Internal.ModelCompatibilityChecker.CompatibleWithModel(InternalContext internalContext, ModelHashCalculator modelHashCalculator, Boolean throwIfNoMetadata, DatabaseExistenceState existenceState) +160
System.Data.Entity.Internal.InternalContext.CompatibleWithModel(Boolean throwIfNoMetadata, DatabaseExistenceState existenceState) +102
System.Data.Entity.Database.CompatibleWithModel(Boolean throwIfNoMetadata, DatabaseExistenceState existenceState) +57
System.Data.Entity.CreateDatabaseIfNotExists'1.InitializeDatabase(TContext context) +206
System.Data.Entity.Internal.<>c__DisplayClassf'1.<CreateInitializationAction>b__e() +165
System.Data.Entity.Internal.InternalContext.PerformInitializationAction(Action action) +110
System.Data.Entity.Internal.InternalContext.PerformDatabaseInitialization() +660
System.Data.Entity.Internal.LazyInternalContext.<InitializeDatabase>b__4(InternalContext c) +31
System.Data.Entity.Internal.RetryAction'1.PerformAction(TInput input) +143
System.Data.Entity.Internal.LazyInternalContext.InitializeDatabaseAction(Action'1 action) +292
System.Data.Entity.Internal.LazyInternalContext.InitializeDatabase() +123
System.Data.Entity.Internal.InternalContext.Initialize() +42
System.Data.Entity.Internal.InternalContext.GetEntitySetAndBaseTypeForType(Type entityType) +39
System.Data.Entity.Internal.Linq.InternalSet'1.Initialize() +137
System.Data.Entity.Internal.Linq.InternalSet'1.get_InternalContext() +38
System.Data.Entity.Infrastructure.DbQuery'1.System.Linq.IQueryable.get_Provider() +99
System.Linq.Queryable.Where(IQueryable'1 source, Expression'1 predicate) +63
PortalRH.WebUI.Controllers.UsuarioController.Index(Usuario usuario) in c:\Users\renilson.meneguci\Documents\Visual Studio 2013\Projects\UEM_ES\Pronim LC Web\AS1311D01_01\Main\Fontes\GovBr_PRONIM_LCnet\PortalRH.WebUI\Controllers\UsuarioController.cs:126
lambda_method(Closure , ControllerBase , Object[] ) +180
System.Web.Mvc.ActionMethodDispatcher.Execute(ControllerBase controller, Object[] parameters) +59
System.Web.Mvc.ReflectedActionDescriptor.Execute(ControllerContext controllerContext, IDictionary'2 parameters) +434
System.Web.Mvc.ControllerActionInvoker.InvokeActionMethod(ControllerContext controllerContext, ActionDescriptor actionDescriptor, IDictionary'2 parameters) +60
System.Web.Mvc.Async.ActionInvocation.InvokeSynchronousActionMethod() +76
System.Web.Mvc.Async.AsyncControllerActionInvoker.<BeginInvokeSynchronousActionMethod>b__39(IAsyncResult asyncResult, ActionInvocation innerInvokeState) +36
System.Web.Mvc.Async.WrappedAsyncResult'2.CallEndDelegate(IAsyncResult asyncResult) +73
System.Web.Mvc.Async.WrappedAsyncResultBase'1.End() +136
System.Web.Mvc.Async.AsyncResultWrapper.End(IAsyncResult asyncResult, Object tag) +102
System.Web.Mvc.Async.AsyncControllerActionInvoker.EndInvokeActionMethod(IAsyncResult asyncResult) +49
System.Web.Mvc.Async.AsyncInvocationWithFilters.<InvokeActionMethodFilterAsynchronouslyRecursive>b__3d() +117
System.Web.Mvc.Async.<>c__DisplayClass46.<InvokeActionMethodFilterAsynchronouslyRecursive>b__3f() +323
System.Web.Mvc.Async.<>c__DisplayClass33.<BeginInvokeActionMethodWithFilters>b__32(IAsyncResult asyncResult) +44
System.Web.Mvc.Async.WrappedAsyncResult'1.CallEndDelegate(IAsyncResult asyncResult) +47
System.Web.Mvc.Async.WrappedAsyncResultBase'1.End() +136
System.Web.Mvc.Async.AsyncResultWrapper.End(IAsyncResult asyncResult, Object tag) +102
   System.Web.Mvc.Async.AsyncControllerActionInvoker.EndInvokeActionMethodWithFilters(IAsyncResult asyncResult) +50
System.Web.Mvc.Async.<>c__DisplayClass2b.<BeginInvokeAction>b__1c() +72
System.Web.Mvc.Async.<>c__DisplayClass21.<BeginInvokeAction>b__1e(IAsyncResult asyncResult) +185
System.Web.Mvc.Async.WrappedAsyncResult'1.CallEndDelegate(IAsyncResult asyncResult) +42
System.Web.Mvc.Async.WrappedAsyncResultBase'1.End() +133
System.Web.Mvc.Async.AsyncResultWrapper.End(IAsyncResult asyncResult, Object tag) +56
System.Web.Mvc.Async.AsyncControllerActionInvoker.EndInvokeAction(IAsyncResult asyncResult) +40
System.Web.Mvc.Controller.<BeginExecuteCore>b__1d(IAsyncResult asyncResult, ExecuteCoreState innerState) +34
System.Web.Mvc.Async.WrappedAsyncVoid'1.CallEndDelegate(IAsyncResult asyncResult) +70
System.Web.Mvc.Async.WrappedAsyncResultBase'1.End() +139
System.Web.Mvc.Async.AsyncResultWrapper.End(IAsyncResult asyncResult, Object tag) +59
System.Web.Mvc.Async.AsyncResultWrapper.End(IAsyncResult asyncResult, Object tag) +40
System.Web.Mvc.Controller.EndExecuteCore(IAsyncResult asyncResult) +44
System.Web.Mvc.Controller.<BeginExecute>b__15(IAsyncResult asyncResult, Controller controller) +39
System.Web.Mvc.Async.WrappedAsyncVoid'1.CallEndDelegate(IAsyncResult asyncResult) +62
System.Web.Mvc.Async.WrappedAsyncResultBase'1.End() +139
System.Web.Mvc.Async.AsyncResultWrapper.End(IAsyncResult asyncResult, Object tag) +59
System.Web.Mvc.Async.AsyncResultWrapper.End(IAsyncResult asyncResult, Object tag) +40
System.Web.Mvc.Controller.EndExecute(IAsyncResult asyncResult) +39
   System.Web.Mvc.Controller.System.Web.Mvc.Async.IAsyncController.EndExecute(IAsyncResult asyncResult) +39
System.Web.Mvc.MvcHandler.<BeginProcessRequest>b__5(IAsyncResult asyncResult, ProcessRequestState innerState) +39
System.Web.Mvc.Async.WrappedAsyncVoid'1.CallEndDelegate(IAsyncResult asyncResult) +70
System.Web.Mvc.Async.WrappedAsyncResultBase'1.End() +139
System.Web.Mvc.Async.AsyncResultWrapper.End(IAsyncResult asyncResult, Object tag) +59
System.Web.Mvc.Async.AsyncResultWrapper.End(IAsyncResult asyncResult, Object tag) +40
System.Web.Mvc.MvcHandler.EndProcessRequest(IAsyncResult asyncResult) +40
System.Web.Mvc.MvcHandler.System.Web.IHttpAsyncHandler.EndProcessRequest(IAsyncResult result) +38 System.Web.CallHandlerExecutionStep.System.Web.HttpApplication.IExecutionStep.Execute() +9715856
System.Web.HttpApplication.ExecuteStep(IExecutionStep step, Boolean& completedSynchronously) +155