sqldatareader

问题 I'm reading back a bit value from an SQL table, and casting as a boolean value to map to a boolean model value. But when I read back the IsPDLChecked bit field and initialise as false, I get an index out of range exception . I looked up the definition of the exception and I'm not sure why the value is out of range due to it being init with a false value , ie, 0 . So it's not a negative range value. Question: Why am I getting an IndexOutOfRange exception although the bit value being read back

问题 I am trying to use a SqlDataReader to run a query and then display the results in a messagebox, but I keep getting the error Invalid attempt to read when no data is present. Here is my code. public void button1_Click(object sender, EventArgs e) { string results = ""; using (SqlConnection cs = new SqlConnection(@"Server=100-nurex-x-001.acds.net;Database=Report;User Id=reports;Password=mypassword")) { cs.Open(); string query = "select stationipaddress from station where stationname = @name";

问题 I realized I always read my fields in the order they are returned by index (using constants). So my code is already compatible with CommandBehavior.SequentialAccess as far as i understand. Would there be any benefits if i turn it on? DataReader is already forward only, read only which is the real performance gain right? 回答1: The main usage of this is when you are reading very large CLOB ( nvarchar(max) etc) or BLOB ( varbinary(max) ) fields. In the default usage, it buffers the entire row of

问题 I realized I always read my fields in the order they are returned by index (using constants). So my code is already compatible with CommandBehavior.SequentialAccess as far as i understand. Would there be any benefits if i turn it on? DataReader is already forward only, read only which is the real performance gain right? 回答1: The main usage of this is when you are reading very large CLOB ( nvarchar(max) etc) or BLOB ( varbinary(max) ) fields. In the default usage, it buffers the entire row of

问题 Is it not possible to get the return value of a stored procedeure when using a datareader? The return value is always null, but the SP returns a valid int from within SSMS. myCommand.CommandText = "GetVenueVideos"; SqlParameter retVal = new SqlParameter("@returnValue",SqlDbType.Int); retVal.Direction = ParameterDirection.ReturnValue; myCommand.Parameters.Add(retVal); myReader = myCommand.ExecuteReader(); if (myReader.Read() && myReader.HasRows) { int returnValue = Convert.ToInt32(retVal.Value

问题 I have a windows form that I am asking a user to enter a pcname in textbox1 and then trying to use SqlDataReader to the read from the database to get the pc ipaddress and then map the pc drive to my local pc. But for some reason when I use the textbox within the SQL parameter it's not working. But when I replace the textbox1.text with the actual pcname it works fine. Hopefully someone can help me find out why the parameter isn't working correctly. Here is my code: public void button1_Click

问题 This is the code I' using for reading data from sql through DataReader. It gives Error when there is a NULL in table. How to handle it? I tried c.ActualWeight= dr[0] as float? ?? default(float); The problem with this is that it is successful in Handling NULLs but the result is Always 0 even if the sql database has value 1 in that field. { List<Inventory_Connector> LC = new List<Inventory_Connector>(); string ConString = "data source=DELL\\SQLSERVER1;Initial Catalog=Camo;Integrated Security

问题 What's the difference between reading a value from an SqlDataReader using this syntax: Dim reader As SqlClient.SqlDataReader reader("value").ToString() OR Dim reader As SqlClient.SqlDataReader reader.GetString(reader.GetOrdinal("value")) 回答1: I think that the reason to use GetOrdinal() is so that you can cache the result and re-use it multiple times for performance. E.g. Dim reader As SqlClient.SqlDataReader int valueOrdinal = reader.GetOrdinal("value"); while ( ... ) { var value = reader

问题 I'm creating a booking management system and I am having problems trying to get data from a SQL database and insert into a group of textboxes of my application. I want to show the customer details, when a button is clicked, in a DataGridView, but when I click the button, the application throws an exception with the following error message; Invalid attempt to read when no data is present. I have attached a screenshot of the screen where I want to view customer details, and the code for the

问题 I'm creating a booking management system and I am having problems trying to get data from a SQL database and insert into a group of textboxes of my application. I want to show the customer details, when a button is clicked, in a DataGridView, but when I click the button, the application throws an exception with the following error message; Invalid attempt to read when no data is present. I have attached a screenshot of the screen where I want to view customer details, and the code for the