如果使用SQL，返回我的函数将不起作用

Question

I am populating a text box with the returned value of a function, but it doesn't work if I run the sql code inside the function. I can remove the sql related code and it works. so i'm stumped.

And by "doesn't work" i mean that the text box never gets populated with anything. it remains blank.

thanks

public string CreateResident()
{
    string result = "hmm";
    SqlConnection sqlConnection = new SqlConnection("Server=DELLXPS\\SQLEXPRESS; Initial Catalog=Warren_SEINDATASYSTEMS; Integrated Security=true;");
    SqlCommand cmd = new SqlCommand();

    cmd.CommandText = "INSERT INTO [dbo].[NewUsers]([ResidentAccountNumber],[ResidentName],[ResidentAddress],[NumberOfVisitors],[TempPass],[Role])VALUES(@ResidentAccountNumber,@ResidentName,@ResidentAddress,@NumberOfVisitors,(select cast((Abs(Checksum(NewId()))%10) as varchar(1)) + char(ascii('a')+(Abs(Checksum(NewId()))%25)) + char(ascii('A')+(Abs(Checksum(NewId()))%25)) + left(newid(),5)),'resident')";
    cmd.CommandType = CommandType.Text;
    cmd.Connection = sqlConnection;

    SqlParameter ResidentAccountNumber = new SqlParameter();
    ResidentAccountNumber.ParameterName = "@ResidentAccountNumber";
    ResidentAccountNumber.Value = txtboxResidenetAccountNumber.Text.Trim();
    cmd.Parameters.Add(ResidentAccountNumber);
    SqlParameter ResidentName = new SqlParameter();
    ResidentName.ParameterName = "@ResidentName";
    ResidentName.Value = txtboxResidentName.Text.Trim();
    cmd.Parameters.Add(ResidentName);
    SqlParameter ResidentAddress = new SqlParameter();
    ResidentAddress.ParameterName = "@ResidentAddress";
    ResidentAddress.Value = txtboxResidentAddress.Text.Trim();
    cmd.Parameters.Add(ResidentAddress);
    SqlParameter NumberOfVisitors = new SqlParameter();
    NumberOfVisitors.ParameterName = "@NumberofVisitors";
    NumberOfVisitors.Value = txtboxNumberOfVisitors.Text.Trim();
    cmd.Parameters.Add(NumberOfVisitors);


    try
    {
        sqlConnection.Open();
        result = (string)cmd.ExecuteScalar();
        sqlConnection.Close();
    }
    catch (Exception ex)
    {
        result = ex.Message;
    }

    return result;
}

protected void btnCreateResident_Click(object sender, EventArgs e)
{
    txtboxTempPassword.Text = CreateResident();
}

Answer 1

Your SQL is wrong and you have a lot of problems but I want to show you a way to make your code more readable. Format it like this:

cmd.CommandText = @"INSERT INTO [dbo].[NewUsers] ([ResidentAccountNumber],[ResidentName],[ResidentAddress], NumberOfVisitors],[TempPass], Role])
                    VALUES(
                      @ResidentAccountNumber,
                      @ResidentName,
                      @ResidentAddress,
                      @NumberOfVisitors,
                      (select cast((Abs(Checksum(NewId()))%10) as varchar(1)) + char(ascii('a')+(Abs(Checksum(NewId()))%25)) + char(ascii('A')+(Abs(Checksum(NewId()))%25)) + left(newid(),5)),
                      'resident')";
cmd.CommandType = CommandType.Text;
cmd.Connection = sqlConnection;

We know that a select in a VALUES constructor is not legal so that is one problem.

Also having a SELECT without a from seems strange -- did you copy your code correctly?

You are using ExecuteScalar -- do you know what that does? It shouldn't include a query that includes INSERT query.

I'm guessing you probably want a stored procedure.

Answer 2

I would suggest do not write query in C# code, you must use Stored Procedure for the same purpose. If you want your query to return some id, primary key or some value then you must write query for that after your insert query. you can use the following keywords in your select query,if you want to return id from table.

SCOPE_IDENTITY returns the last IDENTITY value inserted into an IDENTITY column in the same scope.

IDENT_CURRENT returns the last identity value generated for a specific table in any session and any scope.

@@IDENTITY returns the last identity value generated for any table in the current session, across all scopes.

If you want to return only one record then use ExecuteScalar else you can use ExecuteReader .

If your only purpose is to insert data into the table then you should use ExecuteNonQuery .

Answer 3

With the help of comments I went with ExecuteReader instead of the ExecuteScaler . And changed the statement to return a value

INSERT INTO [table] ([fields]) OUTPUT Inserted.MyColumn VALUES(values)

C# Code:

    reader = cmd.ExecuteReader();
    try
    {
        while (reader.Read())
        {
            result = reader[0].ToString();
        }
    }
    catch (Exception ex)
    {
        result = ex.Message;
    }

    return result;