检查值是否在 SQL Server 数据库中并显示在消息中

Question

这是插入数据的BL类：

public  string CategoryIsert(clsCategoryPL objCategory, out int returnId)
{
    returnId = 0;

    try
    {
        var db = new KSoftEntities();

        var category = new tblCategory
        {
            Name = objCategory.Name,
            ParentCategoryID = objCategory.ParentCategoryID,
            description = objCategory.description,
            image = objCategory.image,
            Status = objCategory.Status
        };

        //db.AddTotblCategories(category);
        db.tblCategories.Add(category);
        db.SaveChanges();
        returnId = category.CategoryID;
    }
    catch (Exception ex) { }

    if (returnId > 0)
         return "User Inserted Successfully";
     else
         return "Error on insertion";
}

增值的aspx代码：

private int AddCategory()
{
    clsCategoryBL objcategory = new clsCategoryBL();
    clsCategoryPL objCategoryPL = new clsCategoryPL();

    int retnid = 0;

    objCategoryPL.description = txtCategoryDescription.Text;
    objCategoryPL.Name = txtCategoryName.Text;
    objCategoryPL.ParentCategoryID = Convert.ToInt32(ddlParentCategory.SelectedValue);
    objCategoryPL.Status = true;

    objcategory.CategoryIsert(objCategoryPL, out retnid);

    if (retnid > 0)
    {
        if (Convert.ToInt32(ddlParentCategory.SelectedValue) == 0)
        {
              objCategoryPL.ParentCategoryID = retnid;
        }

        objCategoryPL.CategoryID = retnid;
        string strMessage = objcategory.CategoryUpdate(objCategoryPL);
    }

    return retnid;
 }

我在数据库中创建了一个存储过程：

CREATE PROCEDURE [dbo].[Sp_Checknm_Cat]
   @ID int,
   @NAME nvarchar(400),
   @Count INT = 0
AS
BEGIN
    DECLARE @output int

    IF(@ID > 0)
    BEGIN
        SET @Count = (select count(*) from tblCategory 
                      where Name = @NAME and CategoryID <> @ID)
    END
    ELSE
    BEGIN
        SET @Count = (select count(*) from tblCategory where Name = @NAME)
    END

    IF(@Count > 0)
    BEGIN
        SET @output = 0 
    END
    ELSE
    BEGIN
        SET @output = 1 
    END

    RETURN @output
END

我想在插入/更新期间检查该名称是否已经存在，然后它会在标签中显示一条错误消息

那么哪里需要改变呢？

这是给 bl 的：

 ClsDB objdb = new ClsDB();
 public Int32 InsertnmCheck(int id, string nm)
 {
     DataTable dtdonor = new DataTable();
     SqlParameter[] param = new SqlParameter[2];

     param[0] = new SqlParameter("@ID", SqlDbType.Int);
     param[0].Direction = ParameterDirection.Input;
     param[0].Value = id;

     param[1] = new SqlParameter("@NAME", SqlDbType.NVarChar);
     param[1].Direction = ParameterDirection.Input;
     param[1].Value = nm;

     int a = objdb.insert_delete_update("[Sp_Checknm_Cat]", param);
     return a;
 } 

这是我的后端代码：

else if (btnSubmit.CommandName == "Add")
{
   clsCategoryBL obj = new clsCategoryBL();
   Int32 dt = obj.InsertnmCheck(0, txtCategoryName.Text);
   //   DataTable dt = obj.InsertnmCheck(0, txtCategoryName.Text);

   {

   }

   int retid = AddCategory();
   if (retid > 0)
   {
   }

问题是查询（sp）返回 0 但在 bl 类中它将返回 -1 那么有什么解决办法吗？？

Answer 1

抛出异常。

CREATE PROCEDURE [dbo].[usp_Checknm_Cat] /* do not prefix with 'sp' */
@ID int,
@NAME nvarchar(400),
@Count INT=0

AS
BEGIN
DECLARE @output int


    if(@ID>0)
    begin
        set @Count= @Count + (select count(*) from tblCategory where Name=@NAME and CategoryID<>@ID)
    end
    else
    begin
        set @Count= @Count + (select count(*) from tblCategory where Name=@NAME)
    end


    if(@Count>0)
    BEGIN;
      THROW 51000, 'Duplicates Exist', 1;
    END;


END

和c#

public void /* VOID, not a return code or return string */ CategoryIsert(clsCategoryPL objCategory)
{

    try
    {
        var db = new KSoftEntities();

        var category = new tblCategory
        {
            Name = objCategory.Name,
            ParentCategoryID = objCategory.ParentCategoryID,
            description = objCategory.description,
            image = objCategory.image,
            Status = objCategory.Status
        };

        //db.AddTotblCategories(category);
        db.tblCategories.Add(category);
        db.SaveChanges();
        returnId = category.CategoryID;
    }
    catch (SqlException sqlex) {
           /* you can examine the sql exception here, if you want to look for the 51000 */
           throw;
 }


    catch (Exception ex) {
           throw;
 }


}