How can I prevent a combobox value from being selected more than once?

Question

I need your help please.

I have this method:

protected void btnDocumentType_Click(object sender, EventArgs e)
        {

            DocumentApplicationCategoryManager DACM = new DocumentApplicationCategoryManager();
            IkubInfo.NE.Domain.DocumentApplicationCategory DAC = new Domain.DocumentApplicationCategory();

            DAC.DocumentType = new DocumentTypeManager().GetById(new Guid(cboDocumentType.SelectedValue));
            DAC.ApplicationCategory = Entity;

            Entity.DocumentApplicationCategory.Add(DAC);

            DACM.Save(DAC);
            DACM.Session.CommitChanges();
            SetUIValues();
        }

This is the method for the ADD button, which allows the user to add a value in the grid. I need to check that if the value that the user is trying to add is saved once, it cannot be saved twice. I need to validate it and show user an error message but I don't know how to do this. I guess that I have to put an "if" condition before this line:

DAC.DocumentType = new DocumentTypeManager().GetById(new Guid(cboDocumentType.SelectedValue));

Any idea ? Your help would be appreciated. Thanks in advance :)

Answer 1

protected void btnDocumentType_Click(object sender, EventArgs e)
        {

            DocumentApplicationCategoryManager DACM = new DocumentApplicationCategoryManager();
            IkubInfo.NE.Domain.DocumentApplicationCategory DAC = new Domain.DocumentApplicationCategory();

            DAC.DocumentType = new DocumentTypeManager().GetById(new Guid(cboDocumentType.SelectedValue));
            DAC.ApplicationCategory = Entity;

//Check here from DocumentApplicationCategory, Whether DAC.DocumentType and Entity Exists or not, if does not exists then allow to come in 
        if(CHECK_HERE)
        {
                Entity.DocumentApplicationCategory.Add(DAC);

                DACM.Save(DAC);
                DACM.Session.CommitChanges();
        }
            SetUIValues();
        }

refer the comments: at place of CHECK_HERE, Put your condition to confirm the data your are trying to insert already exists or not.

Answer 2

What you need to do is to check for every value in the combobox if the value inserted exists or not. To do so, you need to create a loop with a condition of type HasNext or IsNull and inside th loop you will use your If statement that will compare the values of the ID (from what i have understood from your code) .