数据库正在正确更新，但出现错误

我当前的代码给了我以下错误，第一个是当我添加记录时，第二个是当我删除或更新记录时。在这些实例中，数据库仍然正确更新

为了进一步解释，我可以添加像XXX这样的东西，它在开始时不在数据库中，即使数据库更新了，我也得到了错误#1。当我删除该条目时，数据库更新，得到错误#2。如果我返回并再次插入XXX，数据库更新，我再次得到错误#1。

编辑#2，我确实注意到在数据库中，UNIQUE KEY列跳过数字，所以我可以添加VVV，错误1发生，它得到136的UNIQUE KEY。然后添加VUV，得到错误#1,UNIQUE KEY为138

违反UNIQUE KEY约束AK_DimCurrency_CurrencyAlternateKey。不能在对象dbo.DimCurrency中插入重复键。重复键值为(XXX)，语句终止。

IListSource不包含任何数据源。

public partial class Default : System.Web.UI.Page
{
    SqlConnection vid = new SqlConnection("Data Source=(LocalDB)''v11.0;AttachDbFilename=''AdventureWorksDW_Data.mdf;Integrated Security=True;Connect Timeout=30");
    static DataTable dtDataForGrid = new DataTable();
    protected void Page_Load(object sender, EventArgs e)
    {
    }
    protected void ButtonSearch_Click(object sender, EventArgs e)//on button click the database connection is opened and the query is executed if possible, if not error will display on label 1
    {
        LabelError.Text = "";
        try
        {
            string str = TextBox1.Text;
            SqlCommand xp = new SqlCommand(str, vid);
            vid.Open();
            xp.ExecuteNonQuery();
            SqlDataAdapter da = new SqlDataAdapter();
            da.SelectCommand = xp;
            DataSet ds = new DataSet();
            da.Fill(ds);
            GridView1.DataSource = ds;
            GridView1.DataBind();
            vid.Close();
        }
        catch (Exception c)
        {
            LabelError.Text = (c.Message);
        }
    }
    protected void ButtonReset_Click(object sender, EventArgs e)//resets the page, if error, it will display at label 1
    {
        try
        {
            Response.Redirect("~/Default.aspx");
        }
        catch (Exception c)
        {
            LabelError.Text = (c.Message);
        }
    }
    protected void DropDownList1_SelectedIndexChanged(object sender, EventArgs e)//drop down list that adds text depending on choice to reduce redundant typing in multiple executions
    {
        if (DropDownList1.SelectedIndex == 1)
        {
            TextBox2.Text = "INSERT INTO";
            TextBox3.Text = " VALUES";
            TextBox4.Text = "";
            TextBox4.Enabled = false;
        }
        if (DropDownList1.SelectedIndex == 2)
        {
            TextBox2.Text = "UPDATE";
            TextBox3.Text = " SET";
            TextBox4.Text = " WHERE";
            TextBox4.Enabled = true;
        }
        if (DropDownList1.SelectedIndex == 3)
        {
            TextBox2.Text = "DELETE FROM";
            TextBox3.Text = " WHERE";
            TextBox4.Text = "";
            TextBox4.Enabled = false;
        }
    }
    protected void ButtonChange_Click(object sender, EventArgs e)//executes the operation from textbox2, and 3.
    {
        LabelError2.Text = "";//resets the label to nothing before changing the text again if needed below
        LabelFullOperation.Text = "";//resets the label to nothing before changing the text again if needed below
        if (TextBox4.Text == null)//sets the label6 text to textbox 2 and 3, unless 4 has text, in which case 2, 3, and 4 will be used
        {
            LabelFullOperation.Text = TextBox2.Text + TextBox3.Text;
        }
        else
        {
            LabelFullOperation.Text = TextBox2.Text + TextBox3.Text + TextBox4.Text;
        }
        try
        {
            string str = TextBox2.Text + TextBox3.Text + TextBox4.Text;//gets the text from textboxes 2, 3, adn 4, if any
            SqlCommand xp = new SqlCommand(str, vid);
            vid.Open();
            xp.ExecuteNonQuery();
            SqlDataAdapter da = new SqlDataAdapter();
            da.SelectCommand = xp;
            DataSet ds = new DataSet();
            da.Fill(ds);
            GridView1.DataSource = ds;
            GridView1.DataBind();
            vid.Close();
        }
        catch (Exception c)
        {
            LabelError2.Text = (c.Message);
        }
    }

xp.ExecuteNonQuery();

da.Fill(ds);