c# - 无效的转换异常，没有重定向或警报

Question

我有一个返回 OutRes 的 SQL 过程

protected void LoginButton_Click1(object sender, EventArgs e)
{
  int Results = 0;

  using (SqlConnection sc1 = new SqlConnection())
  {
    sc1.ConnectionString = "Data Source=localhost;Initial Catalog=Drug;Integrated Security=True";
    SqlCommand sqlcom = new SqlCommand("user_login",sc1);
    {
        sqlcom.CommandType = CommandType.StoredProcedure;
        sqlcom.Parameters.Add("@UsernameSP", SqlDbType.VarChar, 10).Value = this.txtUserName.Text.Trim();
        sqlcom.Parameters.Add("@PasswordSP", SqlDbType.VarChar, 10).Value = this.txtPwd.Text.Trim();
        sqlcom.Parameters.Add("@OutRes", SqlDbType.VarChar, 4);
        sqlcom.Parameters["@OutRes"].Direction = ParameterDirection.Output;
        sqlcom.Connection = sc1;

        try
        {
            sc1.Open();
            sqlcom.ExecuteNonQuery();
            Results =(int)sqlcom.Parameters["@OutRes"].Value;
        }
        catch (SqlException ex)
        {
            ScriptManager.RegisterClientScriptBlock(this, this.GetType(), "alertMessage", "alert('" + ex.Message + "')", true);
        }
        finally
        {
            sqlcom.Dispose();
            if (sc1 != null)
            {
                sc1.Close();
            }

        }
    } 
    if (Results == 0)
    ScriptManager.RegisterClientScriptBlock(this, this.GetType(), "alertMessage", "alert('" + "result 0" + "')", true);
    else
     { 
     ScriptManager.RegisterClientScriptBlock(this, this.GetType(), "alertMessage", "alert('" + "result 1" + "')", true);
     Response.Redirect("/DrugEntry.aspx");
     }
}

1. 此处无效转换异常:

   "结果 =(int)sqlcom.Parameters["@OutRes"].Value;System.InvalidCastException 未被用户代码处理Message=指定的转换无效"

2. 该代码不显示警报或重定向。发生了什么事？

---

这不会显示。根据我的查询，我的结果变量存储为 0 或 1。

if (Results == 0)
    ScriptManager.RegisterClientScriptBlock(this, this.GetType(), "alertMessage", "alert('" + "result 0" + "')", true);
else
{ ScriptManager.RegisterClientScriptBlock(this, this.GetType(), "alertMessage", "alert('" + "result 1" + "')", true);
Response.Redirect("DrugEntry.aspx");
}

两个警报都没有显示。知道为什么吗？

Answer 1

您需要将 @Outres Parameter 的类型从 Varchar 更改为 Int。

protected void LoginButton_Click1(object sender, EventArgs e)
{
  int Results = 0;
  using (SqlConnection sc1 = new SqlConnection())
  {
      sc1.ConnectionString = "Data Source=localhost;Initial Catalog=Drug;Integrated Security=True";
      SqlCommand sqlcom = new SqlCommand("user_login",sc1);
      {
         sqlcom.CommandType = CommandType.StoredProcedure;
         sqlcom.Parameters.Add("@UsernameSP", SqlDbType.VarChar, 10).Value = this.txtUserName.Text.Trim();
         sqlcom.Parameters.Add("@PasswordSP", SqlDbType.VarChar, 10).Value = this.txtPwd.Text.Trim();
         sqlcom.Parameters.Add("@OutRes", SqlDbType.Int, 4);
         sqlcom.Parameters["@OutRes"].Direction = ParameterDirection.Output;
         sqlcom.Connection = sc1;

         try
         {
           sc1.Open();
           sqlcom.ExecuteNonQuery();
           Results =(int)sqlcom.Parameters["@OutRes"].Value;

         }
         catch (SqlException ex)
         {
              ScriptManager.RegisterClientScriptBlock(this, this.GetType(), "alertMessage", "alert('" + ex.Message + "')", true);

         }
         finally
         {
            sqlcom.Dispose();
            if (sc1 != null)
            {
               sc1.Close();
            }

        }
    } 
    if (Results == 0)
       ScriptManager.RegisterClientScriptBlock(this, this.GetType(), "alertMessage", "alert('" + "result 0" + "')", true);
    else
    { 
       ScriptManager.RegisterClientScriptBlock(this, this.GetType(), "alertMessage",   "alert('" + "result 1" + "')", true);
       Response.Redirect("/DrugEntry.aspx");
    }
 }