How to make taxonomy picker required when used in visual web part?

Question

I have created a visual web part in which user has to specify a field's value from taxonomy picker control. I want to make that value mandatory. The control is placed successfully but when I use the <asp:requieredfieldvalidator> it throws error.

My code is:

<Taxonomy:TaxonomyWebTaggingControl runat="server" 
        ID="taxProjectOwnerDepartment" Visible="true" IsMulti="false" IsDisplayPickerButton="true">
            </Taxonomy:TaxonomyWebTaggingControl>
        <asp:RequiredFieldValidator ID="rfvProjectOwnerDepartment" runat="server" ControlToValidate="taxProjectOwnerDepartment"
             ErrorMessage="Please Specfiy Owner's Department" ForeColor="Red" Display="Dynamic" />

The log shows this

What should I do?

Answer 1

change your code to:

<Taxonomy:TaxonomyWebTaggingControl runat="server" ID="taxProjectOwnerDepartment" Visible="true" IsMulti="false" IsDisplayPickerButton="true">
</Taxonomy:TaxonomyWebTaggingControl>

<asp:CustomValidator ID="rfvProjectOwnerDepartment" runat="server"  OnServerValidate="validator_ServerValidate" />

now in your codebehind add the new method validator_ServerValidate:

    protected void validator_ServerValidate(object source, System.Web.UI.WebControls.ServerValidateEventArgs args)
    {
        string errorMessage = "Please Specfiy Owner's Department";
        if (!taxProjectOwnerDepartment.Validate(out errorMessage))
        {
            args.IsValid = false;
            rfvProjectOwnerDepartment.ForeColor = ConsoleColor.Red;
            rfvProjectOwnerDepartment.Display = ValidatorDisplay.Dynamic;
            rfvProjectOwnerDepartment.ErrorMessage = errorMessage;
        }
    }

the value of taxonomy is stored in a hidden input field so its not really a input field and throws an error when calling ControlToValidate="taxProjectOwnerDepartment" unfortunatly

Is it possible to have a required field validator for Taxonomy webtagging control

EDIT

For issues with empty input you need to add:

if(e.Value.Length == 8)
{
    e.IsValid = true;
}
else
{
    e.IsValid = false;
}

so code will look like this:

    protected void validator_ServerValidate(object source, System.Web.UI.WebControls.ServerValidateEventArgs args)
    {
        string errorMessage = "Please Specfiy Owner's Department";

        if(e.Value.Length == 0)
        {
             args.IsValid = false;
             rfvProjectOwnerDepartment.ForeColor = ConsoleColor.Red;
             rfvProjectOwnerDepartment.Display = ValidatorDisplay.Dynamic;
             rfvProjectOwnerDepartment.ErrorMessage = errorMessage;
        }
        else
        {
            if (!taxProjectOwnerDepartment.Validate(out errorMessage))
            {
               args.IsValid = false;
               rfvProjectOwnerDepartment.ForeColor = ConsoleColor.Red;
               rfvProjectOwnerDepartment.Display = ValidatorDisplay.Dynamic;
               rfvProjectOwnerDepartment.ErrorMessage = errorMessage;
            }
        }
    }

so now we have changed the codebehind to first check if the length is correct (not 0) if its isnt 0 then do check what was entered to validate! code is a bit bulky, you could change it so that the if function is in one checking with an or statment like this:

    protected void validator_ServerValidate(object source, System.Web.UI.WebControls.ServerValidateEventArgs args)
    {
        string errorMessage = "Please Specfiy Owner's Department";

            if (e.Value.Length == 0 || !taxProjectOwnerDepartment.Validate(out errorMessage))
            {
               args.IsValid = false;
               rfvProjectOwnerDepartment.ForeColor = ConsoleColor.Red;
               rfvProjectOwnerDepartment.Display = ValidatorDisplay.Dynamic;
               rfvProjectOwnerDepartment.ErrorMessage = errorMessage;
            }
    }