c# - MySQL 和 SQL Server 的 IDbCommand 命名参数

Question

我一直在尝试创建一些独立于数据库的代码，如下所示:

IDbCommand command = connection.CreateCommand();
command.CommandText = "...";

IDbDataParameter param1 = command.CreateParameter();
param1.ParameterName = "param1";
param1.Value = "value";
command.Parameters.Add(param1);

适用于 mysql 的命令文本是:

select * from mytable where field1 = ?param1

适用于 sqlserver 的命令文本是:

select * from mytable where field1 = @param1

是否有某种形式对两者都适用？

编辑:

• SQL Server 2008R2
• MySQL 5.0.X

Answer 1

不，我认为没有这样的方法。所以你必须提供你自己的:

public static String GetProviderParameter(string paramName, IDbConnection con)
{
    string prefix = "";
    if(con is System.Data.SqlClient.SqlConnection)
        prefix = "@";
    else if(con is System.Data.OleDb.OleDbConnection)
        prefix =  "?";
    else if(con is System.Data.Odbc.OdbcConnection)
        prefix =  "?";
    else if(con is MySql.Data.MySqlClient.MySqlConnection)
        prefix =  "?";

    return prefix + paramName;
}

用法:

param1.ParameterName = GetProviderParameter("param1", connection);

或者您可以使用 this使用反射来使用 DbCommandBuilder 类中的 protected 方法 GetParameterName 的扩展:

public static class Db
{
    static readonly Func<DbConnection, DbProviderFactory> getDbProviderFactory = 
        (Func<DbConnection, DbProviderFactory>)Delegate.CreateDelegate(typeof(Func<DbConnection, DbProviderFactory>), typeof(DbConnection).GetProperty("DbProviderFactory", BindingFlags.Instance | BindingFlags.NonPublic).GetGetMethod(true));
    static readonly Func<DbCommandBuilder, string, string> getParameterName =
        (Func<DbCommandBuilder, string, string>)Delegate.CreateDelegate(typeof(Func<DbCommandBuilder, string, string>), typeof(DbCommandBuilder).GetMethod("GetParameterName", BindingFlags.Instance | BindingFlags.NonPublic, Type.DefaultBinder, new Type[] { typeof(string) }, null));

    public static DbProviderFactory GetProviderFactory(this DbConnection connection)
    {
        return getDbProviderFactory(connection);
    }

    public static string GetParameterName(this DbConnection connection, string paramName)
    {
        DbCommandBuilder builder = GetProviderFactory(connection).CreateCommandBuilder();

        return getParameterName(builder, paramName);
    }
}

那么就很简单了:

param1.ParameterName = connection.GetParameterName("param1");