how to check if stored procedure exists or not in sql server using c# code

Try:

if exists(select * from sys.objects where type = 'p' and name = '<procedure name>' )

Also you can check that with c#:

string connString = "";
string query = "select * from sysobjects where type='P' and name='MyStoredProcedureName'";
bool spExists = false;
using (SqlConnection conn = new SqlConnection(connString))
{
    conn.Open();
    using (SqlCommand command = new SqlCommand(query, conn))
    {
        using (SqlDataReader reader = command.ExecuteReader())
        {
            while (reader.Read())
            {
                spExists = true;
                break;
            }
        }
    }
}

For those who use Entity Framework and a DbContext:

create an extension class for DbContext:

internal static class DbContextExtensions
{
    public static bool StoredProcedureExists(this DbContext context,
        string procedureName)
    {
        string query = String.Format(
            @"select top 1 from sys.procedures " +
              "where [type_desc] = '{0}'", procedureName);
        return dbContext.Database.SqlQuery<string>(query).Any();
    }
}

As robIII remarked, this code should not be published to the outside world as it makes the database vulnerable for hackers (thank you RobIII!). To prevent this use a parameterized statement. The problem with the above mentioned method is described here

The solution is to put procedureName as a parameter in an SQL statement. SQL will check if the string parameter has the desired format, thus inhibiting malicious calls:

public static bool ImprovedExists(this DbContext dbContext, string procedureName)
{
    object[] functionParameters = new object[]
    {
        new SqlParameter(@"procedurename", procedureName),
    };
    const string query = @"select [name] from sys.procedures where name= @procedurename";
    return dbContext.Database.SqlQuery<string>(query, functionParameters).Any();
}

I found this on MSDN

select * from sys.objects where type_desc = 'SQL_STORED_PROCEDURE' AND name = 'Sql_PersonInsert'