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Future installments will explore more advanced updating scenarios, such as customizing the Grid View's editing interface and programmatically setting the updated values. The UPDATE Table Name SET Column Name1 = @Parameter Value1 Column Name2 = @Parameter Value2 ...Column Name N = @Parameter Value N WHERE Primary Key Column Name1 = @Primary Key Value To Update1 AND Primary Key Column Name2 = @Primary Key Value To Update2 AND ...You either never assigned something to the variable, never created an instance of the value assigned to the variable, or you set the variable equal to Nothing/null manually, or you called a function that set the variable to Nothing/null for you. You don’t have to use the “new” keyword, but by default the value is Nothing/null.You would have to at least initialize to a = String. Again, this is code that C# will not compile, but VB. Same as a string, any reference type must be initialized.This article is one in a series of articles on ASP. In particular, we look at enabling editing support in the Grid View. This article focuses on the Sql Data Source control; for a detailed look at updating with the Object Data Source, refer to the "Editing, Inserting, and Deleting" tutorials in my Working with Data in ASP. Let's explore the updating "action" for the Access Data Source and Sql Data Source controls in more detail. NET 2.0 introduces three new data Web controls: the Grid View, the Details View, and the Form View.
The Web Form also included a Button whose method, thereby kicking off the inserting workflow.With the Sql Data Source control's , and so forth). If you are configuring this information via the Update Query property from the Properties window, then your screen should look like the following: Select Command="SELECT [Product ID], [Product Name], [Products].[Category ID], [Category Name], [Unit Price], [Discontinued] FROM [Products] INNER JOIN [Categories] ON [Products].[Category ID] = [Categories].[Category ID] ORDER BY [Product Name]" Update Command="UPDATE [Products] SET [Product Name] = @Product Name, [Category ID] = @Category ID, [Unit Price] = @Unit Price, [Discontinued] = @Discontinued WHERE [Product ID] = @Product ID" Note that each parameter in the Update Parameters collection is a Parameter object.Recall that when using manually-created Web Forms in the inserting and deleting scenarios, we would use Control Parameter objects that referenced the particular Web control that held the parameter's value.Empty, or to some other actual value, before it will compile in C#, or run without exception in VB. Net, set [a = “something”] before you attempt to do anything with it. Strings and some other CTS types have a misconception of being value types, like Integers, and they are not.A more complex example would be that you disposed of a class that maybe you use to access the database. But then, somewhere else, you tried to call a method of that class that used those objects that no longer exists.
Net: You are trying to use a reference variable who’s value is Nothing/null.