RunspaceConfiguration psConfig = RunspaceConfiguration.Create();
Runspace psRunspace = RunspaceFactory.CreateRunspace(psConfig);
psRunspace.Open();
using (Pipeline psPipeline = psRunspace.CreatePipeline())
            {

            // Define the command to be executed in this pipeline
            Command command = new Command("Add-spsolution");

            // Add a parameter to this command
            command.Parameters.Add("literalpath", @"c:\project3.wsp");

            // Add this command to the pipeline 
            psPipeline.Commands.Add(command);


                // Invoke the cmdlet
            try
            {
                Collection<PSObject> results = psPipeline.Invoke();
                Label1.Text = "hi"+results.ToString();
                // Process the results
            }
            catch (Exception exception)
            {
                Label1.Text = exception.ToString();// Process the exception here
            }

        }

It is throwing the exception:

System.Management.Automation.CommandNotFoundException: The term 'add-spsolution' is not recognized as the name of a cmdlet, function, script file, or operable program.

Any suggestions why?