ado.net

问题 I wants to know whether there is any limit for number of rows that we can add to datatable. I am doing this in C# and .NET 2005. Actually my application is reading large text file around 40 MB,application reads text file line by line and adds it as row in datatable once all file reads then calls update method to update data to database. I am not sure how many rows we can add to datatable. I just want to make my application secure from throwing any error in future if file size again increase.

问题 This is my table: Student : StudentId int PK autoincrement,Name varchar(20) When i am trying to update last added records then i am geting error: Error : Concurrency violation: the UpdateCommand affected 0 of the expected 1 records. This is my code: using (var connection = new SqlConnection("MyConnectionstring")) { connection.Open(); SqlDataAdapter adapter = new SqlDataAdapter(); SqlCommandBuilder builder = new SqlCommandBuilder(adapter); adapter.SelectCommand = new SqlCommand("select * from

问题 Is it possible? Please note I am not using LINQ nor Entity Framework. 回答1: You could also check out Dapper-Dot-Net - a very lightweight and very capable "micro ORM" which - incidentally - is used to run this site here. It's quite fast, a single *.cs file, works with your usual T-SQL commands and returns objects - works like a charm, it's very fast, very easy to understand, no big overhead - just use it and enjoy! 回答2: My personal favorite is done using the dynamic object featured in .NET4 via

问题 I am creating a MVC 6 project and I would rather use Classic ADO.net over Entity Framework 7. However It is saying that name space can not be found for both DataTable and SqlDataAdapter . I have a using System.Data and System.Data.SqlClient statement. It dose not show an error until I try to build the project. I think I read somewhere that those two names spaces are not implemented in the new version. If so is there an alternative way of doing it or am I missing a dependency or using

问题 I typically write my SQL as so in .NET sql.Append("SELECT id, code, email FROM mytable WHERE variable = @variable "); Then do something like this: using (SqlConnection conn = new SqlConnection(ConfigurationManager.ConnectionStrings[ConfigurationManager.AppSettings["defaultConnection"]].ConnectionString)) { using (SqlCommand myCommand = new SqlCommand(sql.ToString(), conn)) { myCommand.Parameters.AddWithValue("@variable", myVariableName"); ... But should I also do this addParameter when the

问题 I'm trying to determine at runtime what the SqlDbType of a sql server table column is. is there a class that can do that in System.Data.SqlClient or should I do the mapping myself? I can get a string representation back from SELECT DATA_TYPE, CHARACTER_MAXIMUM_LENGTH FROM INFORMATION_SCHEMA.COLUMNS WHERE TABLE_CATALOG = '{0}' AND TABLE_SCHEMA = '{1}' AND TABLE_NAME = '{2}' AND COLUMN_NAME = '{3}' EDIT: I can't use SMO as I have no control over the executing machine so I can't guarantee it

问题 There are so many different options coming out of microsoft for data access. Which one is the best for scalable apps? Linq Should we be using Linq? It certainly seems easy but if you know your SQL does it really help. Also I hear that you can't run Async queries in ASP.NET using Linq. Therefore I wonder if it is really scalable? Are there any really big sites using Linq (With the possible exception of stackoverflow). Entity Framework Don't hear so much razzmatazz about the Entity Framework.

问题 MySQL SQL commands can contain user variables that start with '@'. The MySQL ADO.NET connector also uses '@' for command parameters. Is there a way to escape the '@' character so I can use a user-variable in an SQL statement sent to MySQL via ADO.NET? I'm trying to do something like this: UPDATE company SET next_job_id = @jobid:=next_job_id+1 WHERE company_id = @companyid; SELECT @jobid; Where @jobid is a MySQL user variable and @companyid is a parameter. 回答1: It's a connection string option

问题 I have the following LINQ query: var timesheets = from timesheet in entities.Timesheets join timesheetTask in entities.Timesheet_Task on timesheet.Id equals timesheetTask.Timesheet_Id join task in entities.Tasks on timesheetTask.Task_Id equals task.Id join project in entities.Projects on task.Project_Id equals project.Id join department in entities.Departments on project.Department_Id equals department.Id where timesheet.Employee_Id == employeeId select new { date = timesheet.Date, taskName =

问题 I am trying to pass a table name as a parameter to my query through SqlCommand but it doesn't seems to be working. Here is my code; SqlConnection con = new SqlConnection( "server=.;user=sa;password=12345;database=employee" ); con.Open( ); SqlCommand cmd = new SqlCommand( "drop table @tbName" , con ); cmd.Parameters.AddWithValue( "@tbName" , "SampleTable" ); cmd.ExecuteNonQuery( ); con.Close( ); 回答1: SqlCommand.Parameters are supported for Data manipulation language operations not Data