C# 如果第一个查询结果=第二个查询结果

我尝试使用If语句进行两个查询。如果查询1=查询2

string select = "Select ProfileId from Project_list Where ProjectId = @ProjectId";
        using (SqlConnection myConnection = new SqlConnection(connectionString))
        {

            myConnection.Open();
            SqlCommand myCommand = new SqlCommand(select, myConnection);
            myCommand.Parameters.AddWithValue("@ProjectId", querystring);
            object Project_listResult = myCommand.ExecuteScalar();
        }


        string getProfileId = "SELECT ProfileId FROM User_Profile WHERE UserId = (@UserId)";
        using (SqlConnection myConnection = new SqlConnection(connectionString))
        {
            myConnection.Open();
            SqlCommand myCommand = new SqlCommand(getProfileId, myConnection);
            myCommand.Parameters.AddWithValue("@UserId", currentUserId);
            object User_profileResult= myCommand.ExecuteScalar();
        }


        if (Project_listResult == User_profileResult)
        {
            addFollowerButton.Visible = true;

        }

这是我的代码，但不起作用

错误18当前数据库中不存在名称“Project\u listResult”

---

错误19当前数据库中不存在名称“User_profileResult”

如果我了解您正在尝试比较对象。所以你得试试

 if (Project_listResult.Equals(User_profileResult))
            addFollowerButton.Visible = true;

---

您必须在外部定义这两个值，以便在范围内使用它们。现在，您正在使用中定义这两个值，因此这些值仅在only-under的范围内，在该范围之外不可用，因此您将得到该错误

一个简单的建议是，在使用select作为变量名时，避免使用属于不同语言的关键字。这有助于提高可读性并增加混乱

object Project_listResult = null;
object User_profileResult = null;
using (SqlConnection myConnection = new SqlConnection(connectionString))
        {

            myConnection.Open();
            SqlCommand myCommand = new SqlCommand(select, myConnection);
            myCommand.Parameters.AddWithValue("@ProjectId", querystring);
            Project_listResult = myCommand.ExecuteScalar();
        }


        string getProfileId = "SELECT ProfileId FROM User_Profile WHERE UserId = (@UserId)";
        using (SqlConnection myConnection = new SqlConnection(connectionString))
        {
            myConnection.Open();
            SqlCommand myCommand = new SqlCommand(getProfileId, myConnection);
            myCommand.Parameters.AddWithValue("@UserId", currentUserId);
            User_profileResult= myCommand.ExecuteScalar();
        }


        if (Project_listResult.Equals(User_profileResult))
        {
            addFollowerButton.Visible = true;

        }