将 SQL 参数集合传递给函数

Question

When writing ASP.NET CRUD applications in C#, I often find myself inserting a lot of repetitive boilerplate codes for fetching SQL Server queries into data tables, fetching scalar values from queries into variables, calling stored procedures, and so forth.

Recently, I've been trying to refactor this by creating generic classes and methods to handle these basic tasks. However, in order for these to work properly, they need to be able to take an arbitrary number of parameters. The built-in SqlParameterCollection class seemed the obvious first choice, but unfortunately this class cannot be instantiated from user code. The next option was to pass a List<SqlParameter> to the function, and then use foreach to add its contents to the built-in parameter collection of the SqlCommand . This worked, but the declaration is a bit clumsy.

To create the list in code before calling the function, I have to do something like this:

List<SqlParameter> ParameterList = new List<SqlParameter>
{
    new SqlParameter() { ParameterName = "@Parameter1", SqlDbType = SqlDbType.VarChar, Value = InputVariable1 },
    new SqlParameter() { ParameterName = "@Parameter2", SqlDbType = SqlDbType.VarChar, Value = InputVariable2 },
    new SqlParameter() { ParameterName = "@Parameter3", SqlDbType = SqlDbType.VarChar, Value = InputVariable3 }
};

This is hard to read on smaller monitors and still contains a lot of repetitious boilerplate. So my next step was to create a custom class with an overloaded Add method so that this would not be needed. I've read that it is bad to subclass List in C#, so I used Collection instead:

public class ParameterCollection : Collection<SqlParameter>
{
    public void Add(string    ParameterName,
                    SqlDbType ParameterType,
                    object    ParameterValue)
    {
        // Create the parameter and add it to the list
        SqlParameter Parameter = new SqlParameter();
        Parameter.ParameterName = ParameterName;
        Parameter.SqlDbType     = ParameterType;
        Parameter.Value         = ParameterValue;
        base.Add(Parameter);

        // Done
        return;
    }
}

I can then declare a parameter collection like this:

ParameterCollection Parameters = new ParameterCollection
{
    // name          type               value
    { "@Parameter1", SqlDbType.VarChar, InputVariable1 },
    { "@Parameter2", SqlDbType.VarChar, InputVariable2 },
    { "@Parameter3", SqlDbType.VarChar, InputVariable3 }
};

My question is this: Is there any quicker/easier way to perform this task that I'm overlooking? And are there any potential hidden pitfalls or bad practices in the way I'm currently doing it?

Answer 1

您可能忽略的一件事是Add返回Add的参数，这允许我们在同一语句中设置值：

cmd.Parameters.Add("@Parameter1", SqlDbType.VarChar).Value = paramValue;

Answer 2

Rather than instantiating and passing a collection—which, as you say, is hampered by SqlParameterCollection having no public constructor—you may pass the collection indirectly, by passing the SqlCommand itself. Your generic classes and methods may then add parameters to SqlCommand.Parameters , removing the need for you to instantiate a separate collection.

Answer 3

There are several ways to perform this action.

First: You must declare the new parameter.

cmd.Parameters.Add("@Parameter1", SqlDbType.VarChar, 50 //the size of Varchar);

Then you add the value.

cmd.Parameters["@Parameter1"].Value = paramValue;

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