判断用户名是否重复 asp.net access
if (Page.IsValid)
{
string a = username.Text;
string sql;
sql = "select * from userdetail where username='" + this.username.Text + "'";//建立sql查询语句
OleDbConnection conn = new OleDbConnection("Provider=Microsoft.Jet.OLEDB.4.0; Data Source=" + Server.MapPath("./App_Data/db1.mdb"));//建立数据库连接
conn.Open();
OleDbCommand cmd = new OleDbCommand(sql, conn);
int count = Convert.ToInt32(cmd.ExecuteScalar ());
if (count > 0)//如果数据中没有记录或有多条记录则抱错
{
return;
}
else
{
}
conn.Close();
提示红色错误,说输入字符格式不正确,我该怎么转换,用的是文字