System.Reflection.TargetException: Non-static method requires a target.
   at System.Reflection.RuntimeMethodInfo.CheckConsistency(Object target)
   at System.Reflection.RuntimeMethodInfo.InvokeArgumentsCheck(Object obj, BindingFlags invokeAttr, Binder binder, Object[] parameters, CultureInfo culture)
   at System.Reflection.RuntimeMethodInfo.Invoke(Object obj, BindingFlags invokeAttr, Binder binder, Object[] parameters, CultureInfo culture)
   at System.Reflection.RuntimePropertyInfo.GetValue(Object obj, Object[] index)
   at System.Data.Entity.Core.Objects.ELinq.QueryParameterExpression.TryGetFieldOrPropertyValue(MemberExpression me, Object instance, Object& memberValue)
   at System.Data.Entity.Core.Objects.ELinq.QueryParameterExpression.TryEvaluatePath(Expression expression, ConstantExpression& constantExpression)
   at System.Data.Entity.Core.Objects.ELinq.QueryParameterExpression.EvaluateParameter(Object[] arguments)
   at System.Data.Entity.Core.Objects.ELinq.ELinqQueryState.GetExecutionPlan(Nullable`1 forMergeOption)
   at System.Data.Entity.Core.Objects.ObjectQuery`1.<>c__DisplayClass41_0.<GetResults>b__1()
   at System.Data.Entity.Core.Objects.ObjectContext.ExecuteInTransaction[T](Func`1 func, IDbExecutionStrategy executionStrategy, Boolean startLocalTransaction, Boolean releaseConnectionOnSuccess)
   at System.Data.Entity.Core.Objects.ObjectQuery`1.<>c__DisplayClass41_0.<GetResults>b__0()
   at System.Data.Entity.SqlServer.DefaultSqlExecutionStrategy.Execute[TResult](Func`1 operation)
   at System.Data.Entity.Core.Objects.ObjectQuery`1.GetResults(Nullable`1 forMergeOption)
   at System.Data.Entity.Core.Objects.ObjectQuery`1.<System.Collections.Generic.IEnumerable<T>.GetEnumerator>b__31_0()
   at System.Data.Entity.Internal.LazyEnumerator`1.MoveNext()
   at System.Linq.Enumerable.FirstOrDefault[TSource](IEnumerable`1 source)
   at smsoffice.Infra.CustomerManager.GetCustomerByApiKey(String key) in C:\Users\Levan\source\repos\__workspace__\smsoffice\smsoffice\Infra\Customer\CustomerManager.cs:line 396
   at api_getBalance_Default.HandleRequest() in C:\Users\Levan\source\repos\__workspace__\smsoffice\smsoffice\api\getBalance\Default.aspx.cs:line 26
   at api_getBalance_Default.Page_Load(Object sender, EventArgs e) in C:\Users\Levan\source\repos\__workspace__\smsoffice\smsoffice\api\getBalance\Default.aspx.cs:line 12