Edytuj

Udostępnij za pośrednictwem

Executing a command

  • Artykuł

Applies to: .NET Framework .NET .NET Standard

Download ADO.NET

The Microsoft SqlClient Data Provider for SQL Server has SqlCommand object that inherits from DbCommand. This object exposes methods for executing commands based on the type of command and desired return value, as described in the following table.

Command Return Value
ExecuteReader Returns a DataReader object.
ExecuteScalar Returns a single scalar value.
ExecuteNonQuery Executes a command that does not return any rows.
ExecuteXMLReader Returns an XmlReader. Available for a SqlCommand object only.

Each strongly typed command object also supports a CommandType enumeration that specifies how a command string is interpreted, as described in the following table.

CommandType Description
Text A SQL command defining the statements to be executed at the data source.
StoredProcedure The name of the stored procedure. You can use the Parameters property of a command to access input and output parameters and return values, regardless of which Execute method is called.
TableDirect The name of a table.

Important

When using ExecuteReader, return values and output parameters will not be accessible until the DataReader is closed.

Example

The following code example demonstrates how to create a SqlCommand object to execute a stored procedure by setting its properties. A SqlParameter object is used to specify the input parameter to the stored procedure. The command is executed using the ExecuteReader method, and the output from the SqlDataReader is displayed in the console window.

static void GetSalesByCategory(string connectionString,
    string categoryName)
{
    using (SqlConnection connection = new SqlConnection(connectionString))
    {
        // Create the command and set its properties.
        SqlCommand command = new SqlCommand();
        command.Connection = connection;
        command.CommandText = "SalesByCategory";
        command.CommandType = CommandType.StoredProcedure;

        // Add the input parameter and set its properties.
        SqlParameter parameter = new SqlParameter();
        parameter.ParameterName = "@CategoryName";
        parameter.SqlDbType = SqlDbType.NVarChar;
        parameter.Direction = ParameterDirection.Input;
        parameter.Value = categoryName;

        // Add the parameter to the Parameters collection.
        command.Parameters.Add(parameter);

        // Open the connection and execute the reader.
        connection.Open();
        using (SqlDataReader reader = command.ExecuteReader())
        {
            if (reader.HasRows)
            {
                while (reader.Read())
                {
                    Console.WriteLine("{0}: {1:C}", reader[0], reader[1]);
                }
            }
            else
            {
                Console.WriteLine("No rows found.");
            }
            reader.Close();
        }
    }
}

Troubleshooting commands

The Microsoft SqlClient Data Provider for SQL Server adds diagnostic counters to enable you to detect intermittent problems related to failed command executions. For more information, see Diagnostic counters in SqlClient.

See also