代码中的表达式术语错误无效

Question

• 错误1'int.TryParse(string,out int)'的最佳重载方法匹配包含一些无效参数

• 错误2参数1:无法从'int'转换为'string'

  它给了我"int.TryParse(surveys.First(),out id)中的错误;"

     L
        var surveys = (from su in DbContext.Surveys
                                 where su.userName == su.userName 
                                 select su.ID);
  if(surveys.Count() > 0)
              {
               int id = 0;
               int.TryParse(surveys.First(), out id);
                 return id;
               }
               return 0;
  

Answer 1

从TryParse()中删除int;

int.TryParse(surveys.First(), out int id);

应该

int.TryParse(surveys.First(), out id);

变化: -

List<SurveyContext> surveys = (from su in DbContext.Surveys
                                          where su.userName == su.userName 
                                          select su.ID).ToList();

至

List<string> surveys = (from su in DbContext.Surveys
                                          where su.userName == su.userName 
                                          select su.ID);

您正在尝试string在Linq中选择类型并将其放入List<SomeType>其中List<int>.

  var surveys = (from su in DbContext.Surveys
                                              where su.userName == su.userName 
                                              select su.ID);

  //Code follows
  int.TryParse(surveys.First(), out id);