Question

我正在N

中提到的Unicode变量名称之前应用

string commandText = @"SELECT AccountType,* 
                          FROM Account 
                          WHERE AccountType LIKE N@input ";

使用以下代码我收到以下错误。需要在这里纠正什么？

例外：列名'N @ input'无效。

    static void Main(string[] args)
    {
        string result = DisplayTest("Daily Tax Updates:  -----------------        Transactions");

    }

    private static string DisplayTest(string searchValue)
    {
        string test = String.Empty;
        string connectionString = "Data Source=.;Initial Catalog=LibraryReservationSystem;Integrated Security=True;Connect Timeout=30";

        using (SqlConnection connection = new SqlConnection(connectionString))
        {
            connection.Open();
            string commandText = @"SELECT AccountType,* 
                          FROM Account 
                          WHERE AccountType LIKE N@input ";
            using (SqlCommand command = new SqlCommand(commandText, connection))
            {
                command.CommandType = System.Data.CommandType.Text;
                command.Parameters.AddWithValue("@input", "%" + searchValue + "%");

                using (SqlDataReader reader = command.ExecuteReader())
                {
                    if (reader.HasRows)
                    {
                        while (reader.Read())
                        {

                            test = reader.GetString(0);
                        }
                    }
                }
            }
        }

        return test;

    }

CODE

{{1}}

Answer 1

我看到一些问题。

   string commandText = @"SELECT AccountType,* 
                              FROM Account 
                              WHERE AccountType LIKE N@input";

应该是

   string commandText = @"SELECT AccountType,* 
                              FROM Account 
                              WHERE AccountType LIKE @input";

...

 command.Parameters.Add("@input",System.Data.SqlDbType.NVarChar,<<size>>);
 command.Parameters[0].Value = "%" + searchValue + "%";

Answer 2

取自此堆栈Stack overflow

SqlParameter parameter = new SqlParameter();
parameter.ParameterName = "@CategoryName";
parameter.SqlDbType = SqlDbType.NVarChar;
parameter.Direction = ParameterDirection.Input;
parameter.Value = categoryName;

Answer 3

我看到你正在尝试使用nvarchar参数。我认为.net默认使用.AddWithValue

我不确定你为什么需要对nvarchar进行类型转换，没有“N”部分你应该没问题。

当您要指定字符串文字应被视为nvarchar而不是varchar时，您需要的那部分，如SELECT * from Table where field like N'%VALUE%'

否则，您只需将变量/参数声明为nvarchar

Answer 4

试试这个 -

private static string DisplayTest(string searchValue)
{
    string connectionString = "Data Source=.;Initial Catalog=LibraryReservationSystem;Integrated Security=True;Connect Timeout=30";

    using (SqlConnection connection = new SqlConnection(connectionString))
    {
        connection.Open();
        string commandText = @"SELECT AccountType,* FROM Account WHERE AccountType LIKE @input";

        using (SqlCommand command = new SqlCommand(commandText, connection))
        {
            command.CommandType = System.Data.CommandType.Text;

            command.Parameters.Add("@input", SqlDbType.NVarChar);
            command.Parameters["@input"].Value = string.Format("%{0}%", searchValue);

            using (SqlDataReader reader = command.ExecuteReader())
            {
                if (reader.HasRows)
                {
                    while (reader.Read())
                    {
                        return reader.GetString(0);
                    }
                }
            }
        }
    }

    return String.Empty;
}

如何将国家字符集应用于动态查询

4 个答案: