So I took over this project and one page is throwing a lot of errors. I would need to refactor the whole thing but as always time is an issue.
In one case the code check's whether a datareader has any rows and if not go to an error page. However as the code is now the datareader can be null (didn't successfully connect to db) and in those cases I can't use
if (!dr.HasRows)
//
becasuse it obviously gives me 'nullreferenceexception was unhandled by code'. I tried with !dr.Read but same thing.
A part of the code is something like
SqlDataReader dr = null;
try
{
//connect to db etc
dr = DbHelper.GetReader("sp_GetCustomer", param);
}
catch
{
//show an error message
}
// and then:
if (!dr.HasRows)
{
}
I have an aspx page which allows a user to submit modified entries into the database, but when the user clicks Submit to fire the stored procedure I want to first run a check to see if a modified row with the same relationship exists.I am passing the results of the following query:
SELECT SwitchRoom.ModifiedID FROM SwitchRoom WHERE SwitchRoomID = @ChkSwitchRmID", constring;
into a DataReader to determine if that relationship exists.I need it to determine whether the reader returns NULL to allow the procedure to execute, if it doesn't, then don't allow the user to save the information.I've tried the following:
if (dbreader = NULL) { Fire Procedure } else { "Error Message" }
and I've even tried passing the reader into a datatable and running it against that without any luck.
public class ProductDetails { private string _productid; public string ProductID { get { return _productid; } } private string _description; public string Description { get { return _description; } } private string _image; public string Image { get { return _image; } } public ProductDetails(string productid, string description, string image) { _productid = productid; _description = description; _image = image; } } public class DataAccess { private static string connectionString = ConfigurationManager.ConnectionStrings["ConnectionString"].ConnectionString; public ProductDetails GetProductDetails() { SqlConnection con = new SqlConnection(connectionString); SqlCommand cmd = new SqlCommand("ProductDetails", con); cmd.CommandType = CommandType.StoredProcedure; string productid = HttpContext.Current.Request.QueryString["productid"]; cmd.Parameters.Add(new SqlParameter("productid", SqlDbType.NVarChar)).Value = productid; con.Open(); SqlDataReader reader = cmd.ExecuteReader(); reader.Read(); ProductDetails pro = new ProductDetails( (string)reader["ProductID"], (string)reader["Description"], (string)reader["Image"]); reader.Close(); return pro; } } protected void PopulateControls() private DataAccess da = new DataAccess(); { ProductDetails product = da.GetProductDetails(); if (product.Description == String.Empty) { lblDescription.Visible = false; } else { lblDescription.Text = product.Description; } }
In the last piece i want to check if the Description field is null or empty in order to hide the label control but i get an error if i write: if (product.Description == DBNull.Value) and can only use ring.Empty. But i want to check for NULL values as well..
I'm having a method that exports content from the database to excel files. The method taks as paramaters a DataReader param and a int param - the number of rows. For the number of rows i'm using a dataset, wich i fill using the same query as for the datareader. So I'm executing it twice... Is there a way I can avoid that? get the number of rows from the datareader?
I am getting an error that an open DataReader associated with this Command, when I'm not using datareader(though probably executereader() is the same thing) how would I close this if I don't have a datareader present?
using (SqlConnection conn = new SqlConnection(ConnectionString)) { SqlCommand cmd = new SqlCommand("spSelectAllTypes",conn); cmd.CommandType = CommandType.StoredProcedure; [code]...
I just want to be able to databind a bunch of dropdownlist in one open connection. (before I had multiple open and closes for each control)
var pq = attributes.SingleOrDefault(a => a.AttributeName == PasswordQuestion").AttributeValue;
The above code will throw an error if null. What is the best way to handle this?The below code would work, but I can't help but feel there's a more graceful way?
I know for a fact that the SQL statement below returns NULL but my code statement "if (obj != null)" is not working.When I debug it I see a value of {} ... not sure what that is. Here is my code:
[Code]....
So, even if SQL returns NULL, it still validates obj as NOT NULL !
Sub Testing(ByVal sender As Object, ByVal e As EventArgs)
If I want to call the Sub from PageLoad event, I wrote like this Testing(nothing,nothing)
Then, in the Sub, I would like to check If Argment is Nothing or not
Dim testID As String If (CType(sender, LinkButton).CommandArgument) = Nothing testID=Request.QuerySting("myID") ELSE testID=(CType(sender, LinkButton).CommandArgument).ToString End If
I get Null error at if statement (If (CType(sender, LinkButton).CommandArgument) = Nothing)
How do you check for null with HtmlAgilityPack? I'm getting "Property or indexer 'HtmlAgilityPack.HtmlNode.HasChildNodes' cannot be assigned to -- it is read only" with the following.
if (Node.Element("TD").HasChildNodes = DBNull.Value)
I"m getting "Object reference not set to an instance of an object. " with
I have a DataTable for which a PrimaryKey constraint has been set to be a combination of an integer column and a datetime column. When I try to 'Find' a row by saying,
dtFunds.Rows.Find(iContainerIndex)
I get a null value. iContainerIndex has been defined as an object array of size 2 with the integer ID and date values in it.
When I set a breakpoint in my code, I see that the very same values are present in the datatable.
If I try to execute, DataTable.Select() method with the integer column filter, I get a result - but returns no result when called with the date column filter.
What am I doing wrong here? The very same DateTime value is present in the datatable.
I am very new to Linq , i want to check if the PrintingAdminSetting table has rows in it and then if it has then i want to get the value and assign it to txtMaxJobs textbox
below is teh code
, please let me know teh syntax to check .
var DC = new ServiceDataContext(); var rec = DC.PrintingAdminSetting.Where("").First(); txtMaxJobs.Text = rec.ParaName.ToString();
I am using Compute for summing up a datatable which has a condition. Sometimes, there are no rows inside the datatable matching my criteria so I get an exception on ComputeObject cannot be cast from DBNull to other types.Is there a way to check/filter the datatable to see if it has the desired rows, if yes only then I apply Compute.
total = Convert.ToDecimal(CompTab.Compute("SUM(Share)", "IsRep=0"));
I have set the value of an int parameter to the attribute of a textbox.The textbox can be empty or null, how to check whether the parameter is empty or null?
Image1,2,3,4 are not a mandatory fields so, when i inserted, i check it if it is not there then i insert null value, Now problem is when i retrive them if there is a row contain image1,2 are image content and 3,4 are null values dataset also filling as it is in database but when i checking like
[code]....
it shows error like
Unable to cast object of type 'System.DBNull' to type 'System.Byte[]'.
Inside a function I need to check to see if a variable value is null, how to do this? I implemented the code but its not returning the value I thought it would return.If it's null I want to set the value of the variable, else I want to query the value from a table
I want this query to return all distinct properties and a thumbnail image. However some properties don't have thumbnail images and they don't get returned by the query. If the imgid is null I still want to return the property. Not sure of how to do this.
I have a query that averages data in 15 minute increments that I display in a chart using Microsoft Chart Controls. Everything works fine except when there is no data for a 15 minute increment. How do I get the chart to show just the empty time slot?
I'm experimenting with validating forms in the asp.net MVC framework. I'm focusing on server side validation for the time being. I've come across an error that I'm not sure how to rectify. System.NullReferenceException: Object reference not set to an instance of an object. The code that throws the error is:
[AcceptVerbs(HttpVerbs.Post)] public ActionResult Create([Bind(Exclude="ID")] MembersCreate mc ) { mc.Modules = ModuleListDataContext.GetModuleList(); ViewData.Model = mc; //Validation using ModelState // // //line below errors when form field is empty // if ((string)mc.Member.Username.Trim() == "") ModelState.AddModelError("Member.Username", "Username is required."); if (!ModelState.IsValid) return View(); try { // TODO: Add insert logic here return RedirectToAction("Index","Home"); } catch { return View(); } }
When I put spaces in the field it performs exactly as i want, but if I leave the field blank and press submit I get the error. What's the best way to avoid this error and still validate blank form fields?
How do I check if my value is empty AND Isnull? I need to check for both, using ISNULL is not enough because the data can change just so that it is empty.
