Question

Call me a ‘n00b’, but I am new to creating Script Controls. I want to create a simple control with 3 text boxes. I have a .cs file that looks like this:

    public class SmokingCalc : ScriptControl     {         public SmokingCalc()         {             Render(htmlWriter);         }         protected override void Render(HtmlTextWriter writer)         {             costTextbox.RenderControl(writer);             base.Render(writer);         }         protected override IEnumerable<ScriptDescriptor>                 GetScriptDescriptors()         {             ScriptControlDescriptor descriptor = new ScriptControlDescriptor('SmokingCalc.SmokingCalc', this.ClientID);             yield return descriptor;         }          // Generate the script reference         protected override IEnumerable<ScriptReference>                 GetScriptReferences()         {             yield return new ScriptReference('SmokingCalc.SmokingCalc.js', this.GetType().Assembly.FullName);         }          protected HtmlTextWriter htmlWriter;         protected TextBox costTextbox;         protected TextBox amountTextbox;         protected TextBox yearsTextbox;         protected Button submitButton;     } } 

and I have absolutely no idea why the textbox wont render? I think I am missing something…

[EDIT] The error I’m getting is the ‘Object reference is not set to an instance to an object’.

[ANSWERED] I changed the file as follows, and it works, so far at least.

   public class SmokingCalc : ScriptControl     {         public SmokingCalc()         {         }         protected override void CreateChildControls()         {             base.CreateChildControls();             costTextbox.ID = 'costTextbox';             amountTextbox.ID = 'amountTextbox';             yearsTextbox.ID = 'yearsTextbox';             submitButton.ID = 'submitButton';             submitButton.Text = 'Submit';             Controls.Add(costTextbox);             Controls.Add(amountTextbox);             Controls.Add(yearsTextbox);             Controls.Add(submitButton);         }         protected override IEnumerable<ScriptDescriptor>                 GetScriptDescriptors()         {             ScriptControlDescriptor descriptor = new ScriptControlDescriptor('SmokingCalc.SmokingCalc', this.ClientID);             descriptor.AddProperty('costTextboxID', costTextbox.ClientID);             descriptor.AddProperty('amountTextboxID', amountTextbox.ClientID);             descriptor.AddProperty('yearsTextboxID', amountTextbox.ClientID);             descriptor.AddProperty('submitButtonID', submitButton.ClientID);             yield return descriptor;         }          // Generate the script reference         protected override IEnumerable<ScriptReference>                 GetScriptReferences()         {             yield return new ScriptReference('SmokingCalc.SmokingCalc.js', this.GetType().Assembly.FullName);         }          protected TextBox costTextbox = new TextBox();         protected TextBox amountTextbox = new TextBox();         protected TextBox yearsTextbox = new TextBox();         protected Button submitButton = new Button();     } 

Answer 1

Did you try CreateChildControls?:

public class SmokingCalc : ScriptControl {     protected override void CreateChildControls()     {         this.Controls.Add(costTextbox);     }      protected override IEnumerable<ScriptDescriptor>             GetScriptDescriptors()     {         ScriptControlDescriptor descriptor = new ScriptControlDescriptor('SmokingCalc.SmokingCalc', this.ClientID);         yield return descriptor;     }      // Generate the script reference     protected override IEnumerable<ScriptReference>             GetScriptReferences()     {         yield return new ScriptReference('SmokingCalc.SmokingCalc.js', this.GetType().Assembly.FullName);     }      protected HtmlTextWriter htmlWriter;     protected TextBox costTextbox = new TextBox();     protected TextBox amountTextbox = new TextBox();     protected TextBox yearsTextbox = new TextBox();     protected Button submitButton = new Button(); }