c# - 如何通过C#修复SQL查询中的错误 'Must declare scalar variable'？

Question

我不断收到这个恼人的错误。我对 SQL 真的很陌生，这实际上是我的第一个查询，但我就是无法让它工作。我已经尝试了几个小时了。请帮忙!

我收到错误:

System.Data.SqlClient.SqlException: 'Must declare the scalar variable "@FirstNamez".

代码:

public static void CreateNewEmployee(string FirstNamez, string LastNamez, int Pinz, string Departmentz)
{
    SqlConnection connection = new SqlConnection();
    connection.ConnectionString = @"Server = localhost\SQLEXPRESS; Database = Employee; Trusted_Connection = True;";

    SqlCommand command = new SqlCommand();

    using (connection)
    {
        connection.Open();
        string commandtext = "INSERT INTO dbo.EmployeeDatabase (FirstName, LastName, PIN, Department) VALUES (@FirstNamez, @Lastnamez, @Pinz, @Departmentz);";

        command.CommandText = commandtext;
        command.Connection = connection;

        command.ExecuteNonQuery();
    }
}

Answer 1

您在查询文本中定义所有参数 - 但您从未设置它们的值!

试试这个:

public static void CreateNewEmployee(string FirstNamez, string LastNamez, int Pinz, string Departmentz)
{
    SqlConnection connection = new SqlConnection();
    connection.ConnectionString = @"Server = localhost\SQLEXPRESS; Database = Employee; Trusted_Connection = True;";

    SqlCommand command = new SqlCommand();

    using (connection)
    {
        connection.Open();
        string commandtext = "INSERT INTO dbo.EmployeeDatabase (FirstName, LastName, PIN, Department) VALUES (@FirstNamez, @Lastnamez, @Pinz, @Departmentz);";

        command.CommandText = commandtext;
        command.Connection = connection;

        // define the parameters and set their values!
        command.Parameters.Add("@FirstNamez", SqlDbType.VarChar, 100).Value = FirstNamez;
        command.Parameters.Add("@LastNamez", SqlDbType.VarChar, 100).Value = LastNamez;
        command.Parameters.Add("@Pinz", SqlDbType.Int).Value = Pinz;
        command.Parameters.Add("@Departmentz", SqlDbType.VarChar, 100).Value = Departmentz;

        command.ExecuteNonQuery();
    }
}