查看:2408|回复：7
各位，麻烦帮忙解答一下：
& && & 我是用VS2010新建了一个website；在APP_CODE文件夹下，
新建了一个有关数据库操作的类SqlOperate.cs：
public class SqlOperate
public SqlOperate()
&&// TODO: Add constructor logic here
& && &&&//
& && && &this.strcon = ConfigurationManager.ConnectionStrings[&constr&].ConnectionS
&&&&public SqlConnection sqlcon()
& && &&&SqlConnection sqlcon = new SqlConnection(strcon);
//建立并返回SqlCommand对象
& & public SqlCommand sqlcom()
& && &&&sqlcon().Open();
& && &&&SqlCommand sqlcom = new SqlCommand();
& && &&&sqlcom.Connection = sqlcon();
& & public SqlCommand sqlcom(String strsql)
& && &&&sqlcon().Open();
& && & SqlCommand sqlcom = new SqlCommand(strsql,sqlcon());
然后在default.cs文件中调用它们：
protected void btSpecialty_Click(object sender, EventArgs e)
& && &&&if ((tbSpecialtyName.Text.Trim() == &&) || (tbSpecialtyRemark.Text.Trim() == &&))
& && && && &string str = &alert('专业名与专业描述不能为空');&;
& && && && &Page.ClientScript.RegisterClientScriptBlock(this.GetType(), &warning&, str, true);
& && &&&else
& && && &&& SqlOperate sql = new SqlOperate();
& && && && & sql.sqlcon().Open();
& && && && &string strsql = &select * from SpecialtyInfo where convert(varchar(255),SpecialtyName)='&+tbSpecialtyName .Text.Trim ()+&'&;
& && && && & if (sql.sqlcom(strsql).ExecuteScalar() != null)
& && && && &{
& && && && && & string str = &alert('该专业已存在，请重新起名');&;
& && && && && & Page.ClientScript.RegisterClientScriptBlock(this.GetType(), &warning&, str, true);
& && && && &}
& && && && &else
& && && && &{
& && && && && & string str2 = &insert into SpecialtyInfo (SpecialtyName,Remark) values ('&+tbSpecialtyName .Text .Trim ()+&','&+tbSpecialtyRemark .Text .Trim ()+&') &;
& && && && && & Specialty sp = new Specialty();
& && && && && & string str3 = sp.addSpecialty(str2);
& && && && && & str3= &alert('添加专业信息成功');&;
& && && && && & Page.ClientScript.RegisterClientScriptBlock(this.GetType(), &warning&, str3, true);
& && && && &}
& && && && &sql.sqlcon().Close();
运行时，出现问题：ExecuteScalar requires an open and available Connection. The connection's current state is closed.&&数据库的连接关闭了。但在上面红色代码中，有调用SqlOperate类的SqlConnection对象的返回方法来获得该对象，再用该对象的Open方法打开；
朋友们，请帮帮忙解答，谢谢。
不要在数据库访问过程中使用js交互。
引用:原帖由 oswica 于
11:11 发表
不要在数据库访问过程中使用js交互。 没有用JS，不知道是不是跟类的对象实例化方面有关，不清楚是不是Connection对象与Command对象的实例不同，导致Connection打开了，但不是Command对应的Connection打开；但后来采用SqlCommand sqlcom = new SqlCommand();
sql.sqlcom(strsql).Connection = sql.sqlcon();
也不能打开数据库连接。
string str = &alert('该专业已存在，请重新起名');&;
& && && && && &&&Page.ClientScript.RegisterClientScriptBlock(this.GetType(), &warning&, str, true);
这个难道不是？
引用:原帖由 oswica 于
13:39 发表
string str = &alert('该专业已存在，请重新起名');&;
& && && && && &&&Page.ClientScript.RegisterClientScriptBlock(this.GetType(), &warning&, str, true);
这个难道不是？ 哦哦，是啊。后来把这段JS代码先注释掉，换成response输出；也依然出现这个问题，连接不了。
//建立并返回SqlCommand对象
& & public SqlCommand sqlcom()
& && &&&sqlcon().Open();
& && &&&SqlCommand sqlcom = new SqlCommand();
& && &&&sqlcom.Connection = sqlcon();
& & public SqlCommand sqlcom(String strsql)
& && &&&sqlcon().Open();
& && & SqlCommand sqlcom = new SqlCommand(strsql,sqlcon());
这2个方法有问题，sqlcon().Open();都已经打开了..sqlcon()这边又打开
换个写法就好了...
public SqlCommand sqlcom(String strsql)
& && &&&SqlConnection sqlcon = new SqlConnection(strcon);
& && &&&sqlcon.Open();
& && &&&SqlCommand sqlcom = new SqlCommand(strsql, sqlcon);
最简单就这样..调用就好了
引用:原帖由 promising123 于
23:27 发表
哦哦，是啊。后来把这段JS代码先注释掉，换成response输出；也依然出现这个问题，连接不了。 这样还是有交互的。
我意思是你将数据获取后在处理或者做判断。IDE :: Operator Requires Either Two Or Three Operands?
Oct 22, 2011
I am in need of help with a project which I am completing.This is what I am currently working with:
If RadioButton1.Checked = True And ComboBox2.Text = &Rate 1& Then Dim Rate(0 To 3) As String
Rate(0) = Math.Round(((85 + (TextBox2.Text - (150 * TextBox1.Text)) * 0.25) / 3) * 100, 0)
Rate(1) = Math.Round((85 + (TextBox2.Text - (150 * TextBox1.Text)) * 0.25) * 100, 0)
Rate(2) = 25
Rate(3) = &F& + TextBox2.Text
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This question already has an answer here:
Here i use my webmethod.But when i going to connect it shows this error.But my code is good i think.
ExecuteReader requires an open and available Connection. The connection's current state is connecting.
public static List&CommonPages& GetCommonPagesDescription(int Type)
List&CommonPages& CommonPageDescription = new List&CommonPages&();
SqlCommand comGetAllFiles = new SqlCommand("GetCommonPageDescriptions", conDB);
mandType = CommandType.StoredP
if (conDB.State == ConnectionState.Closed)
conDB.Open(); // &-- Debugger Skip this & goto next line
comGetAllFiles.Parameters.Add("@Type", SqlDbType.Int);
comGetAllFiles.Parameters["@Type"].Value = T
SqlDataReader rdr = comGetAllFiles.ExecuteReader();//&-- error generating here
DataTable dt = new DataTable();
dt.Load(rdr);
foreach (DataRow r in dt.Rows)
CommonPageDescription.Add(new CommonPages
Id = (int)r["Id"],
Description = r["Description"].ToString(),
Type = (int)r["Type"],
UpdatedDate = (DateTime)r["UpdatedDate"],
UpdatedBy = (Guid)r["UpdatedBy"]
catch (Exception ee)
conDB.Close();
return CommonPageD
conDB Initialized here
static SqlConnection conDB = new SqlConnection(ConfigurationManager.ConnectionStrings["SiteSqlServer"].ConnectionString);
1,43272446
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&asp.net badge can single-handedly close
questions as duplicates and reopen them as needed.
This question has been asked before and already has an answer. If those answers do not fully address your question, please .
Instead of opening the connection when it is closed, try to open the connection when it is not opened.
public static List&CommonPages& GetCommonPagesDescription(int Type)
List&CommonPages& CommonPageDescription = new List&CommonPages&();
SqlCommand comGetAllFiles = new SqlCommand("GetCommonPageDescriptions", conDB);
mandType = CommandType.StoredP
if (conDB.State != ConnectionState.Open)
conDB.Open(); // &-- Debugger Skip this & goto next line
comGetAllFiles.Parameters.Add("@Type", SqlDbType.Int);
comGetAllFiles.Parameters["@Type"].Value = T
SqlDataReader rdr = comGetAllFiles.ExecuteReader();//&-- error generating here
DataTable dt = new DataTable();
dt.Load(rdr);
foreach (DataRow r in dt.Rows)
CommonPageDescription.Add(new CommonPages
Id = (int)r["Id"],
Description = r["Description"].ToString(),
Type = (int)r["Type"],
UpdatedDate = (DateTime)r["UpdatedDate"],
UpdatedBy = (Guid)r["UpdatedBy"]
catch (Exception ee)
conDB.Close();
return CommonPageD
conDB must be a shared connection?
Probably not a good idea, leverage connection pooling.
To fix it, consider opening and closing a connection per request.
Don't care if the voodoo sayers that this inefficient, in truth you want to open/close connections as little as possible but sometimes you need to go to the DB for a single reason.
There are ways you could share a connection better, using a context pattern for example.
But to solve your immediate problem structure your DB calls this way.
using( mon.DbConnection conn = CreateConnection() )
//create your command...
//create your reader/or execute your command...
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