我想检查SQl表中的值，如果存在print lable.text已验证或不验证

Question

DataRow[] rows = dt.Select("verified=yes); // Replace your ColumnName here, it will filter the records
if (rows != null && rows.Count() > 0)
{
    Label2.Text = "already verified";
}
else
{
    Label2.Text = "already not verified";
}

Answer 1

您可以查询DataRow数组：

var exists = (from x in rows
              where x != null
              let col1 = x["columnName"]
              where col1 != DBNull.Value && col1.ToString() == "somevalue"
              select x).Any();


Label2.Text = exists ? "already verified" : "already not verified";

Answer 2

    protected void Button1_Click(object sender, EventArgs e)
    {
        string TabName = TextBox1.Text;

        string cmd = "Data Source=SQL5026;Initial Catalog=DB ...";

        int exists;

            SqlCommand check = new SqlCommand("select case when exists((select * from information_schema.tables where table_name = '" + TabName + "')) then 1 else 0 end",new SqlConnection (cmd));

            check.Connection.Open();
            exists = (int)check.ExecuteScalar();
            if (exists > 0)
            {
                Label1.Text = "OK";
            }
            else
            {
                Label1.Text = "NO";
            }
            }