I have a select string that uses a variable. This variable is defined as a double. I would like to move the connection string from my code-behind to the web config. When I add the connection string

(add key="ConnectionString" value="Select Diameter, Pitch, Quantity, Rotation, Bore, Blades, Material, Manufacturer, Model, Condition from PropInventory where Sold = False and Diameter >= " & myDouble & " Order by Diameter" />)

it tells me that variable myDouble has missing attribute value

How would I declare my variable (as a double)?

That isn't a connection string it is an actual query?

In any event you can't drop variables from XYZ class into your web.config unless you physically write the value to the web.config at run time.

You best bet is to put this query into a stored procedure.

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You could store the value with replacement tokens such as:

<add key="ConnectionString" value="Select Diameter, Pitch, Quantity, Rotation, Bore, Blades, Material, Manufacturer, Model, Condition from PropInventory where Sold = False and Diameter >= ##DIAMETERPARAM## Order by Diameter" />

Then when you actually use this value you simply replace the token with the desired value in the code.

strQuery = ConfigurationManager.ApplicationSettings["ConnectionString"].Replace("##DIAMETERPARAM##", myDouble.ToString());

Alteratively, you could use the String.Format replacement tokens ( {0}, {1}, ...{n} ):

<add key="ConnectionString" value="Select Diameter, Pitch, Quantity, Rotation, Bore, Blades, Material, Manufacturer, Model, Condition from PropInventory where Sold = False and Diameter >= {0} Order by Diameter" />

then you use the standard String.Format method to do the replacement:

strQuery = string.Format(ConfigurationManager.ApplicationSett ings["ConnectionString"], myDouble);

This provide a slightly cleaner line of code, however there is a not an immediate relationship between the string going in (the appsetting value) and the replacement tokens. Using explicit token strings with the .Replace method will make it a bit more readable and maintainable.

-Peter